Yeah, I still remember when Ampex went under. All those tape machines just stopped working! It was chaos.
 
No urgency to replace SONAR here. When it's eventually forced upon me, I'll look around at that time and see what's out there. Studio One 7 should be pretty good by then.

Cactus Music
All the corperate syetms are still W7 and for good reasons. Security and compatability with hardware. I work in a Hospital. We have over a 100 computers all working 100% day in day out doing everything from email to monitoring peoples vitals. All W7. The techs say they will get about another 7 or 8 year out of the OS. 
 
I'm sorely tempted to re install W7 to my main DAW,, but I'd loose the $100 paid for W8.1.

Why would you want to go from Win 8.1 back to Win 7?  Win 8.1 is rock solid, with way more fixes and enhancements than Win 7. That's been my personal experience, and the few benchmarks I saw years ago easily back me up...
 
Now, Win 10 is a whole other story...

Option 3 definitly.
Peace

WRT #1, it may not turn out to be as YUCK as you expect

This is very very sad news I think. Been using Cakewalk since 1992, and bought the lifetime upgrade last year. This just feels wrong :-(
 

I've decided to do a version of option #3.  I have two PC's.  I use one for Internet services and the other is my dedicated DAW.  I'm going to permanently disable Windows 10 updates on the DAW PC.  No need to disconnect from the network since I don't use the net on that box except for DAW specific functions such as plugin downloads and third party recording related updates...i.e. Superior Drummer and the like.

Check out Mixcraft 8 Pro Studio. It is maturing like a fine wine with each new version. At $179 (on sale this weekend for $99), includes side-chaining, VST3 and MP4 support, 64-bit and 32-bit, live recording to performance panel grids and professional video editing. Includes integrated Melodyne Essentials directly into the sound edit tab, and one-click simultaneous publishing to soundcloud, mixcloud, youtube, FB, tumblr and your other music and video sites. Check it out at the Acoustica website.
 
Please allow me to point out the intangibles. We are a small software-only company focusing on the PC (like the early days of Cakewalk). We have a CTO who came from Sonic Foundry and worked on Acid and Vegas, which is why you will see that the Loop Library asset management and video editing are far superior than any other DAW on the market today. Mixcraft 8 is for real!

All is not lost.  How long now have the rabid Ensoniq Paris users have kept that system alive?  It's just software.   It can be reverse engineered, it can be patched, and new drivers can be written to support new hardware.