[K Roche]

I could be wrong but I doubt anybody, weather from Avid or not, can predict 3-5 years into the future with much accuracy

So if your asking if the perpetual license will still work even 3-5 years down the road after letting subscription expire ? the likely answer is, probably Yes, because there is not much of a reason why it wouldn't
But ultimately that is still just somewhat informed speculation based on the fact there isn't much of a practical method, or financial reason for Avid to get into a machine with a frozen perpetual license and somehow block it not to work (if that is even possible) ..

What could happen in the future is Avid could stop selling perpetual licenses altogether and go subscription only ,,,,and perhaps even (albeit extreme) stop allowing annual Support/Upgrade plans for current perpetual licenses. But in either case I doubt they would try to block frozen perpetual licenses from working. Especially since all the user would have to do is simply take the machine off the internet, and there would no possible way Avid cold do anything about a functioning perpetual license...