By the time Carson drops out Cruz will be long gone. Carson is doing much better than Cruz. Carson supporters will go to Trump.
The establishment is divided between Jeb, Rubio and Fiorina. If none of them drops out this will be a cakewalk for Trump. My guess is that Jeb will drop out after the NH primary so that Rubio has a shot at winning Florida.
I dunno 'bout that. Most of the Carson supporters I've seen, both on and off of FR, seem pretty pissy.
Many Trump supporters seem convinced this primary is going to be a cake walk for "the Donald". It won't be. I highly doubt he will be the nominee actually. I also disagree that Carson supporters will go to Trump. I think they represent the "we prefer an outsider, an evangelical preferably, but not Donald Trump". Donald Trump has intense support (which you can see on political forums, etc), but we really don't know how deep it is. Nader had intense support and could fill arena's, but it didn't translate to much national support. McGovern could draw huge rallies in '72, but he got crushed by Nixon. Huge crowds turned out against Walker during the union reform fight, but those crowds did not really represent the majority of Wisconsin voters, etc.
If Trump is generally stuck at around 25%, once the primary is wheedled down to 2 or 3 people one of the others will emerge. I hope it will be Cruz, but there is no sugarcoating he isn't doing very well....yet. So if it isn't Cruz my guess it will end up being Rubio as Jeb is just a bad candidate all around (and I don't think even many "moderate/establishment" voters want another Bush).