Tom Cotton
Ron DeSantis (assuming he doesn't lose re-election in 2022)
Dan Crenshaw (if he builds a following he could probably run straight from the House)
Mike Pence (tries to be the "reasonable" Trump-like candidate)
Nikki Haley (won't get nominated, though)
I also guarantee that at least one right-wing celebrity from Twitter/Fox News runs in 2024 at the true MAGA candidate. Not sure who that would be
I agree and feel that Mike Pence or Tom Cotton would be the most likely candidate in 2024 assuming Trump loses in 2020. As for the candidate from Fox News that would pick up the "MAGA" banner, I would say that either Jeanine Pirro, Sean Hannity, Laura Ingraham, Mark Levin, Steve Doocy, Brian Kilmeade, or Pete Hegseth would make sense, though I don't think that they would have any chance to win the Republican nomination.