Here's a dumb guess with some dumb numbers thrown out.
29% Cruz
24% Trump
12% Rubio
10% Carson
6% Paul
5% Santorum
5% Bush (DISASTER)
3% Huckabee (DISASTER)
3% Christie
2% Fiorina (DISASTER)
1% Kasich
0% Low Energy Losers
Fiorina, Bush, Santorum, and Huckabee all drop out, with Kasich and Paul considering it deeply (Carson plans to stay until South Carolina). Cruz won by a slightly bigger margin than expected, mostly at the expense of Carson. Santorum gets a late bump in Iowa, but not nearly enough to get to anywhere respectable (though he does edge out Bush, rofl lmao). Paul also does better than expected (at Trump's expense), but not nearly enough to get out of a meager fifth place.
Bush isn't dropping out until after NH. His campaign has already made it clear that they're going to politely ignore Iowa (much like McCain did).