I agree that Weidman won't hold the belt long. I think he'd lose for sure against Belfort and the likes of, Bisping, Rockhold, Souza would also stand a good chance of taking the belt.
Add to the mix, Machida, Hendo, Moussasi and Evans could drop down.
Hell, even GSP might fancy a move up if Silva is serious about not fighting for the strap anymore.
Theres just too many seasoned fighters for him to be a long term holder of the belt. I fully expect one of the LHW guys to drop for a title shot.