I'm gonna run through my thoughts.
Why the images are straight from original games: It fits the Superbot style. It's clear in the beta, that a goal with each character is to make them feel like whoever they are in their game. Kratos should feel like he does in God of War. Sly should feel like he does in his games, and so on. So I think ripping the art straight from other games is showing "These our all these characters, straight from your favorite games, all duking it out" It makes sense to me. I even kinda like it
Tekken guys: Alt costumes? Maybe. That would be pretty cool. It would mean characters can expect some pretty cool ones, and plenty. But, in my head it makes more sense for them to just be cameos. I wouldn't put an alt costume on a banner or anything like that. But if there's more to the image it could be so. But for now I would say cameo characters.
Ryu: Didn't expect him at all. Not really familiar with his games, but he looks like a fun character. Doesn't scratch my Mortal Kombat ninja itch though haha.
Roster: I'm predicting the roster to be much larger than people are anticipating. With all the leaks, the roster size is floating around 22. Higher if you count some things we haven't seen. Are there super secret things that wouldn't be in the beta or the official site (until release)? I think so. I'm expecting the launch roster to land around 28 (which I know, would be mind blowingly amazing/awesome) Then after DLC to surpass 30. What can I say? I'm a dreamer.
Evil Cole: I think he's a full playable character. And to be honest, I'm okay with it. I love inFamous and I bet he'll be plenty of fun to play.
Sackboy: WIN
Think I covered everything
Update:
Clank: Can't see him not being with Ratchet. But I wouldn't oppose him as a separate character just because I love the series. But I understand why he should be with Ratchet easy
Final Edit: I think the Tekken guys are alt costumes the more I think about it