You can keep and run any of your older versions on the same machine which is hand.
I just looked at what the updates were for 11 and yeah, a lot of the focus seems to be upgrades to sample editor and functions I dont' really use. I think Artist 11 now has unlimited audio/midi tracks. Don't think 10.5 does. Not that it matters, I have yet to ever max out so don't think i'll be upgrading just for the sake of upgrading.Cubase 10 Pro here. For my uses, I didn’t see anything compelling on 11 for me. I don’t use samples or do scoring and a lot of the new features related to that.