Betfair market gives him odds of around 11-1 to win the nomination. Possible, but not that likely (click link below).
He has odds of around 21-1 to become the next president. Again, this is within the bounds of possibility, but not too likely.
Donald Trump is colourful figure, but the things he says make no sense whatsoever a lot of the time. The likelihood is that he flame out and crash at some point soon as people realize that... well, he's crazy I agree with a journalist that said if Donald wins the nomination then the Republican party will really have jumped the shark.