I think it's still early to call a Trump win. It really depends on what happens with Kasich, Bush, and Carson dropping out if they do. I could see Trump plateauing around where he is now, maybe manage to get another 5-8%, but once this is a three or two way race I can see Rubio, MAYBE even Cruz beating Trump, but the later is unlikely.
The sucky thing for the non-Trumps is that he has a comparatively easy path going forward.
He'll likely see a small bump from South Carolina (maybe a few percent - nothing too gaudy).
He has a formidable lead in Nevada (Rubio is reportedly skipping this state).
He'll likely see another similarly-small bump from Nevada.
Assuming that it's at least a three-way race through Super Tuesday, he wins most of those states.
He gets another larger bump from Super Tuesday domination.
By the time it's a two-person race, he has quite a delegate lead. The antiTrump isn't going to uniformly win everywhere; Trump and this person are going to trade wins - but Trump will already have that delegate lead from the early states. The antiTrump is going to have to win more than 55% of the remaining delegates in order to eeek-out a win.