Nope, just leave it installed if you like.
I'm not sure, but vms8 came with newblue fx, which vsm9 doesn't have. If you uninstall, you'll lose the effects. I don't know if vms7 came with these effects.
Ivan, if you are using V9, you can have V8 installed with Newblue effects. Then install 9, and if you want to, you can then remove V8. Newblue FX will stil be there.