I run SONAR 8.5.3 Producer on Windows 7, and I'm content with it. But I'm wondering whether, as time passes, new software, especially third-party software, will prove incompatible with so old a version of SONAR.
 
Is incompatibility likely to arise? Experienced DAW users, what do you think?
 

if you're asking about 3rd party plugins such as VST effects and VST instruments, then yes, they should always be compatible as long as the 3rd party vendor has adhered to the VST 2 standard.  
 
but if you are going to want to upgrade those VST effects and instruments, there may come a time when vendors stop upgrading VST2 compatibility and go with VST3 only.  that probably won't happen anytime soon, but it might be a problem in the future if you never upgrade from X3 (which does not have VST3 capability).

As far as 3rd party is concerned you're hoping they continue to use a VST version that 8.5.3 understands.

Dang,  that dog is fast..
 

Beagle
if you are going to want to upgrade those VST effects and instruments, there may come a time when vendors stop upgrading VST2 compatibility and go with VST3 only.  that probably won't happen anytime soon, but it might be a problem in the future if you never upgrade from X3 (which does not have VST3 capability).

Thanks. That seems just the kind of situation I'm worried about. One argument for upgrading.

Karyn
As far as 3rd party is concerned you're hoping they continue to use a VST version that 8.5.3 understands.

Thanks. Yes, exactly. So, I gather from your answer and Beagle's, it's something I need to consider.

In addition to being more future proof for externals, the leap from 8.5.3 to Platinum has huge benefits in Sonar itself.  For me, UI and performance improvements alone make it a no-brainer.  That leaves a ton of smooth, sweet stuff on top to make it even better.
 
 

BobF
In addition to being more future proof for externals, the leap from 8.5.3 to Platinum has huge benefits in Sonar itself.  For me, UI and performance improvements alone make it a no-brainer.  That leaves a ton of smooth, sweet stuff on top to make it even better.
 
 

Thanks. Looks like I'm spending the $199, so I'm glad for every additional benefit.

After the initial, likely short, learning curve of the new interface, it's pretty unlikely you'll be disappointed. There's seriously so much great stuff that's been added and improved in the several program generations since 8.5 that it's hard even to know where to begin. 

subtlearts
After the initial, likely short, learning curve of the new interface, it's pretty unlikely you'll be disappointed. There's seriously so much great stuff that's been added and improved in the several program generations since 8.5 that it's hard even to know where to begin. 

Thanks. I just bought it. My learning curve is steeper than average, but I'll hope to get there eventually.