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.
Bitcoin unlimited does have a blocksize limit in practice. It just changes how this limit is decided upon. Instead of the blocksize limit being decided upon by a centralized development team, which is akin to centralized economic planning and obviously flawed, the blocksize limit is determined by the market, miners and users collectively. I believe this does solve the dilemma of governance related to the blocksize issue and possibly other issues in the future as well. I think that Peter R summed up this practical blocksize limit in Bitcoin Unlimited well by saying that:
There exists a natural game-theoretic block size limit.