It will probably be Mahershala Ali, but I voted Dev Patel in the poll. He may have won BAFTA because he's British, and they didn't like Moonlight that much, but with Lion surging at the right time, it could mean something more. Plus, I think he still has good will left from Slumdog Millionaire, and he's in more of his film.
I honestly think either one of the three could win, and I couldn't pick any with any considerable level of certainty, but I will stick with Ali given the SAG win and particularly the speech he gave. It's clear BAFTA liked Lion more than other bodies did, and Patel is British, which lends itself to the idea that he only won because of that. Also, BAFTA clearly didn't like Moonlight as much as AMPAS or any of the American awards bodies, so there's that as well.
Plus that SAG speech...that was something.
"When I'm good, I'm good but when I'm bad I get a serious venereal disease."