Donald Trump has a big delegate lead and popular vote margin with winning margins in the 30% to 40%s. He has little party organization support and few donors. I still the angry plurality existing ITTL. I can see that Cruz is hurt by the discredited Tea Party, but I still see a divided Republican field helping Trump ITTL. The difference is that Kasich is the establishment candidate.
Donald Trump has received 37% of the popular vote thus far, and holds less than a majority of the delegates allocated to this point. As was pointed out above me, the winner take all rules will also be different in 2016, making his route to victory even harder.
Unless of course you're having the GOP in your "TL" be completely incompetent and not actually playing to win.
Not to mention, if Romney isn't the nominee in 2012, it's very realistic for him to come in for the race in 2016, with a majority of the Party knowing him and without the label of a loser, and he could really vie with Trunp here on business credentials and overall qualifications, while using Kasich's OTL "Adult in the Room" strategy combined with actual name recognition.