I doubt Bloomberg will run, he doesn’t have much of a fan base outside of New York City, especially among Republicans. The bigger question is what the RNC will do to guarantee that an establishment figure gets the nomination as Jeb’s numbers continue to stagnate. Will they flail around looking for a last-minute replacement (as Democrats may have to do for Hillary if she’s indicted), or will they just find a way to rig things so that delegates vote for Jeb or a similarly acceptable candidate if things don’t go their way.
Have those "Anybody But [Carter, Clinton, Reagan, McGovern, etc.] movements ever succeeded? When it comes down to saying "We have to beat [so-and-so]," isn't that a sign that one has already lost?
I don't know what will happen or whether Trump can really go the distance, but if he does as well in the primaries as he's doing in the polls now, the nomination is his. That doesn't mean that the convention won't be stormy and tumultuous, with all manner of infighting.