Doesn't XT still have the potential to be activated by miners? Isn't dormant a better word?
Well technically it is. One could argue that as long as a proposal exists there is a chance for it to get activated by miners. If we were talking about probabilities though, it would be very close to null.
I'm reserving judgment about BU. It's possible there's nefarious code in there to steal the bitcoins of ignorant big blockers. I think we can all agree that would be hilarious.
Unlimited blocksize is nefarious by itself. It's like trying to put unlimited cargo on a plane; good luck with that.