In my mind the biggest question is - can Trump can break out of the low 30%. He has been stalled there since the end of September. I can find no new polls the were done after the latest dust up regarding the immigration shut down.
It will be a three way between Cruz, Trump, and one GOPe guy, likely Rubio. Once Cruz loses a few, his supporters will swing to Trump, and it wouldn't shock me to have a March/April announcement that Cruz has accepted a veep position with Trump's campaign.