I see him endorsing Trump in the end, as Trump has consistently spoken up for him against the dirty trick Cruz pulled in Iowa, and showed respect when NBC screwed up the introductions. Carson would never endorse Cruz and I can’t see him as an outsider going for a slick career pol like Rubio.
You must have missed when Trump belittled Dr Carson when he was ahead of Trump in the Iowa polls. That was before the caucus. Trump can’t stand when he is not in first place. Either in the polls in the elections. He acts like a spoiled brat when something doesn’t go his way.