Where on earth could you "recently" buy SONAR 8, and what do you mean by "new copy"? Did you already have one before? Cakewalk-Gibson being out of busines, how could you register it (I assume Bandlab doesn't register those old versions)?
As mentioned above, 8.5 hasn't been available in nearly ten years, and there is no registration transfer method available, so you can't buy second hand versions. Or, of course you can, if you buy registered version and get all the activation keys with it (this goes with 8.5 and older, which only needed one code). I can't see using unauthorized copies of old SONARs as a legal problem in the present situation. Then again, who would need to do so, when CW by Bandlab is free of charge?
I'm also on 8.5 still, and it's enough for me. Upgrading would mean upgrading everything: PC, audio interface, many (most?) of the VSTs etc. Which I can't afford at the moment, so I live in uncertainty - how long will my setup work...