Oddly enough, after the release of the RE6 trailer I find myself coming back to this site. lol.
But... anyway, @topic.
After looking at the massive debate going onto this thread, I gotta say, the guy has a high possibility of being Steve. Or if not, a new character. But either way, Alex Wesker doesn't seem to be a possible candidate for me. Well, for starters, Alex should be evil like Albert was, wouldn't he? And he wouldn't be going around being a mercenary.
Though I've noticed one fact - after looking at the trailer, this new character seems to be superhuman in some way. He's not carrying any weapons, he tackles that zombie in the trailer like a boss, and even goes head to head with a B.O.W. on a somewhat very shabby rooftop. If he were, at all, just an ordinary human, he would be using at least a gun of some sorts. But no. He's carrying none, and he's tackling and punching those zombies like a freaking boss. lol.
Yeah, this evidence might just point out to Alex Wesker because, well, he "is" supposedly superhuman too, but then again, Albert did say that he would bring back Steve "like he was". So apparently Steve being superhuman the moment he returns in the franchise shouldn't really be unexpected. And wow, I really like the comparisons of pictures, it kind of supports this theory a lot more.
As for the girl - I can't really say. Some people say she's voiced by the same VA as Ashley, yet she doesn't "look" older, supposing that a few years had already passed since that incident in Spain with Leon. In fact, she actually does look a bit younger, unless it's the awesome graphics that's playing mind games on me. But nevertheless, even if it was the same VA, there's no certainty as of yet, especially since people can simply recycle VA's in order to save money. And since Ashley's VA sounds like the typical young girl, who would know if it really is a different person.
And I'm pretty curious, I wonder who the woman was that was seemingly blaming herself during the first parts of the trailer. Maybe that's Ashley, considering she did age over the years, and the fact that she was involved in an incident considering infections and whatnot, who would know if she was secretly inserted with a virus of some sort and unintentionally spread the virus the moment she came home. But then again, it's a totally random thought, no evidence. Perhaps it really is her based on the fact that she seems to be talking to Leon (based on context and the flow of the scenes in the trailer), and she looks older than what Sherry should look like (who's probably supposed to be like around... what? Her 20's? But the woman looks a lot older than that in the beginning, so it may have not been Sherry.)
But pretty much - Steve all the way!