It could happen... right now the establishment vote is split, but those voters for Bush and Carson (who is still in it for now), have a low preference for Trump:
https://www.washingtonpost.com/news/the-fix/wp/2016/02/20/where-do-jeb-bush-and-ben-carson-votes-go/

Only 4 out of 33 voters who would vote for Bush or Carson would vote for Trump as the next preference. That isn't very high! On the other hand, their votes get split up between the remaining candidates, so only Katich and Rubio do much better. I think the race will get closer (almost a given anyway as candidates drop out). But I think there will be three at the end--Trump, representing the ticked off voter; Cruz with the religious vote, and Rubio with the establishment bloc... and I think Trump has a good chance of leading a group of three, but possibly losing to a single competitor.