Somehow this category, which was teeming with life pre-nominations, has become lethargic and -- if Stallone wins -- will end up the dullest choice on the year. I guess Rylance and Bale (because of his film's prominence) were always going to be nominees, but I think I'd feel a ton better about the category with wholesale replacement: Elba, Dano, Tremblay, Keaton and Del Toro (all of whom have won or been nominated somewhere) would make a far more exciting slate...not to mention I'd have no idea who might win from that group.
I have to echo Italiano, that if the predicted batch of DiCaprio, Stallone and Vikander all win, it'll be as underwhelming a group of winning performances as we've seen in some time (Brie Larson will be the best by a country mile).
I acknowledge Stallone's standing ovation at the Globes, but I can remember, way back, Fred Astaire getting the same at the '74 Globes (and maybe Lauren Bacall as well? I can't specifically recall, but it seems like it must have happened), so it's not necessarily meaningful -- people might, from nostalgia, salute such a person in the case of a win, but not necessarily be inclined to vote their way. And I agree, it's weird the way what seem signs of weakness -- omissions from SAG and BAFTA -- are somehow being sold as plusses. I guess Stallone's biggest advantage is the lack of coalescing around any one candidate, but maybe that just makes the category a total jump ball -- five candidates about whom no voters are ecstatic, not four plus Stallone.
I'd rate Tom Hardy least likely to win, but, then, I'm less enthusiastic about his performance than many here seem to be. If he wins, it's residual pull from a strong best picture/actor contender, plus, as BJ notes, a big year all around.
Everyone else here seems to be starting with "of course Christian Bale won't win", but I wonder about that. Had he NOT won five years ago, I think he'd be a truly hot contender -- a showy performance in a film right in the thick of the best picture race. And he did have that additional nomination in 2013, so it's not a back-to-back win. I'm not ready to predict him, but I can't say I'd be shocked if his name was called out.
I think Sabin kind of nailed how I feel about Mark Ruffalo: on career profile/film prominence, he seems a solid choice...but I can't say I was wowed by his performance (by me, it's the least impressive of his three in the past six years). However, people liked him enough to nominate him (and not my choice, Keaton), so maybe they'll like him enough to give him the win.
And then there's critics' guy Mark Rylance, who back in December seemed he might run away with it. Hard to tell if he's a Klaus-Maria Brandauer -- the most respectable choice in the group, but not an exciting enough pick to win in the end. Bridge of Spies was fairly popular, especially with the age group that dominates the Oscars, and he might still pull through.
All of which is to say, it could be Stallone on inertia, but, if it's not Stallone, it could be about anybody.