My experience is that the major windows 10 updates (anniversary/creators etc.) have been hosing some device drivers (thunderbolt and nvidia display) and reinstalling the drivers post update has fixed it each time so far. There are not very many things affected and it's annoying but so far not very hard to fix and keep going - this is on my own systems ymmv
 
for the time being I am disabling updates for windows 10 and making system image backups. I can make a full backup turn updates back on and install them and then revert back if there is an issue that can't be fixed. This is more of a problem with windows 10, if you are using windows 7 then the updates are much easier to control and generally less destructive.
 
I am running X1 X2 and X3 on windows 7 systems and not having any problems, I could install my old Sonar 7 and that would work fine too. I used it not too long ago and it's still really cool! That is the first Sonar I ever bought.
 
Yes do take precautions but don't over worry about what might happen. I think it's correct to say that Microsoft is the one thing that could break Sonar but if/when that happens people will be here helping each other out to keep things working. I could be wrong but I think it will keep working for a long time - there are many good options right now to make future upgrade plans without being rushed.
 
Windows 10 will no doubt be making careers out of breaking all kinds of 3rd party softwares along the way regardless of whether they are current and supported, MS breaks their own stuff all the time...that's why/how they make so much money and some of us have jobs as IT people etc  ; p
 
I still like Sonar the best of any daw application, that's why I use it and nothing's going to change that
anytime soon

While I was doomed by 1709 update (screen going blank, like GPU is broken... no, that was just a default change in 1709... note that the screen was blank during initial Windows boot, so BEFORE I could select I want safe mode...), I do not think MS will instantly break things. Yes, they introduce some "bugs", but they try to fix that. A kind of latest Sonar development strategy - can we manage to fix more bugs then we introduce in the fix
 
at least X2 - X3 are still work under Win10 (I have not tried 8.5, but I have heard it also works). I mean why we predict Platinum breaks soon on Win10? Office targeted custom applications (mentioned in the OP post) should not be used as a measure. They are normally developed as fast as possible, using 1000+1 external libraries with questionable compatibility, by "specialists". They can break on any change since they are not build nor tested to survive, written for one-two customers, partially by intention incompatible so the customers need continuous "support" (paid).
 
Internally, VST are pure arithmetical. When written incorrectly, changes in threading model can make them break. That was some recent case with CW plug-ins, and in general that is why in some DAWs the plug-in crash while in other do not. VST are working in multi-threaded environment (RealTime threads for audio processing, GUI and configuration in "main"/"GUI" threads). Plus stupid activation / protection system. But problems can appear even when hosting DAW is still developed, so nothing new/changed by the fact the DAW is frozen.
 
ACT/MackieControl was supported everything as before in X1+. With mods instead of CW. But the same can be written about all internals in Sonar, they was not changed/fixed much since years. So nothing serious has happened 2 weeks ago in that respect a well, we just know nothing will be fixes instead of a hope it will be.

fireberd
I'm a retired LAN/WAN Network and help desk manager (worked for SSA).  Large corporations, federal agencies and even small businesses do not change OS overnight.  It is a huge expense in both the hardware, software and training.  For those reasons, alone, many stay on older OS'.  Its not that the "current" OS is unstable or bad its the $$$.  Take SSA, they have approx. 1800 client server LAN systems in SSA offices and approx. 55,000 "workstations" (PC's).  The PC's run MS Office and specialized applications.  Consider the cost of upgrading the network, and it happened approx. every 10 years while I worked there.

SSA is currently upgrading their desktops to Windows 10...I am currently a contractor there.  The servers we use in my area are moving towards 2016, but not there yet although there are a couple we use at least that are 2012 R2.
 
Fireberd, you are correct in stating that the change over is slow.  Typical for government agencies and rightly so.  I would rather see the slowness than have them rush into changes and have the systems fail to work!
 

I had to roll back to using Windows 7 because my  music computer  Fatally crashed 2x in one year running Windows 10.  I also have a games computer that automatically  zips files and won't allow me access to my emulators.  So I am unhappy with Windows 10 on 2 of my machines.  I really need to take the games computer back to 7 Will Win 7 let me use a machine that has 18 gigs of memory? but it is a lot of work and I haven't felt like doing it.  I continually experience issues with the games machine and I have Virus protection on it too.  Does that sound like a Virus?  Am I the only one experiencing issues from Windows 10 it updates and I lose functionality.

Methodman, your problems are unique to your system(s).  You should make a separate post in the computer section.
 
Depends on which version of Win 7 you have.  If you have Home it will only address 16GB of RAM maximum.  If you have Pro or higher then it will use the full 18GB. 

Cactus Music
Where I work, a hospital, the IT dept is responsible for 1,000 if not 10,000 of computers. They are on Widows 7 and for good reasons. They need control of the OS. They tell me they have no immediate plans to upgrade the 10,000 computers and that W7 is very stable-- if you control it. They test all updates and when they deem them safe they install them. We all have this choice with W7 and as I just found out W8.1. 
So the heart of the problem with W10 is this is very hard to manage and you loose control and things get trashed. 
 

 
I work IT for a very large hospital system as well.  We have over 18,000 computers.  We are mostly Win10.  The misnomer is that you can't control W10, but that is completely false.  The Enterprise edition does not have the "automatic updates", the "store", "cortana" or any of the "home" type of features.  It is very similar to Win7 with less overhead. 
 

There are ways to keep SONAR running for years, yes.
 
But the questions we really need to address here are:
 
1) Do you use your computer for other applications?
2) Are you satisfied with all the current tools SONAR offer?
3) Are you worried new standards might come along that won't be compatible with SONAR?
 
Yes, turning off updates is a solution. But, it is also a security risk, specially nowadays. In my particular case, the answers are:
 
1) Yes, I run other applications on my computer, some that need Windows to be updated so they can run their latest versions, Adobe Cloud being the main one. 
 
2) Yes, I am satisfied, but there are some features I would like to have that it doesn't offer (and likely won't anymore). One of the main ones is the ability to freely customize my I/O setup.
 
3) Yes. More and more we see plug-ins developing particular communication/integration engines that improves workflow, compatibility, and latency. Steinberg will eventually release VST4, Melodyne will improve upon it's ARA, Propellerhead will release revisions to Rewire, and, although there are no immediate plans or needs, MIDI 2 might get developed. These are just some realistic examples, it is also possible that new standards might come along as well.
 
So for me, yes, it is worth upgrading for the reasons I have (not exhaustively) mentioned above.
 
But, if these are not particularly worrisome to you, then I see no reason why you shouldn't be able to continue using SONAR for many years to come. It is a great piece of software and even with Windows rolling out major updates twice a year now, I don't realistically see them interfering with SONAR in a manner that would render it unusable any time soon.

The requirements SONAR lists include Windows 7, so I'm putting together an i5 Intel NUC, based on the Tascam Track Factory idea and using Windows 7. It will be stable, no new features will be added to the Operating System. Once I have it put together, I will create an offline system image so I can restore the working state if needed. 

This will last me a good while. If I do ever switch DAWS, as long as the i5 is powerful enough for the new DAW, I can still use that 'offline' computer as THE System.

While I value the perspective of the IT guys here, it should be noted that IT guys have a naturally pessimistic outlook.
 
I was an IT guy for 15 years. I'm not an IT guy anymore, but I'm now the guy the IT guys call when they're in a jam. So I'm not out of the woods yet, but I do have a longer perspective than most.
 
Back in the 80's I was enroute to a customer visit when I struck up a casual conversation with my seatmate on the plane. He made the comment that he had complete confidence in modern airplanes because "they're all flown by computers nowadays". I didn't say anything because I felt that such a fiction might be important to him, but to myself I thought "that doesn't boost MY confidence one bit!". Because, of course, I spent my days looking at broken and misbehaving computers.
 
Over time, such daily exposure to things that aren't working will naturally result in a general pessimism regarding technology in general. Many of the guys I worked with back then retired to become farmers or something else decidedly low-tech. My own distrust of gadgets and tech dependence will persist forever, I think. 
 
I'm not suggesting all the IT guys are wrong, just a bit overly-pessimistic.
 
I'm sure they'd all protest by saying no, not pessimistic, but realistic. Just being prudent. Prepare for the worst. Buy earthquake insurance. Don't go out after dark. Keep your gun loaded in the nightstand. Wear a face mask in public. Don't touch handrails or use public restrooms, and always wait an hour after lunch before swimming. And who is going to argue against prudence?

Until there is "Windows 11" or whatever that will be called I don't see Sonar being "broken" by Win 10.  Even with "Windows 11" or whatever its called it may still work perfectly.
 
 Just remember "Murphy's Law" applies.
 
50 years working with computers and communications - hardware maintenance/programming/operations - brings me to Murphy's Law.