If that is the final 4, then 3 of them are anti-establishment (at least in perception) and only one, Rubio, is establishment. He might win, but he also doesn't seem very smart, and if you listen to him too long, you can tell he's just spouting rehearsed lines. Cruz, on the other hand, is actually intelligent and sounds relatively spontaneous.
Cruz is absolutely intelligent, even if he is a slimeball. Actually Trump, Carson, and Cruz are all quite intelligent, even though Carson can be pretty flaky. Rubio isn't all that smart. He's got good handlers, so he can appear intelligent if you don't really go after him, but he doesn't appear very good at thinking on his feet, while Trump and Cruz definitely are. I do think those are the final 4, and I think such a scenario favors Trump as long as he doesn't combust due to personality flaws, because Carson and Cruz can come off as even crazier and polarizing than Trump, and Rubio just isn't all that impressive no matter how his handlers and the media try to dress him up.
I don't think that Rubio will win. the reason is that, even though he is the establishment's choice and will have their full backing, and the backing of many 'moderates,' he is a dunce. His rehearsed lines sound good on their own, but closer to the election, if Cruz senses he's the guy to beat, he will start to skewer him in the debates, and Rubio's rehearsed cute anecdotes will be turned into mincemeat. compared to actual arguments from Cruz. That's my prediction.