Im taking a guess that a street fighter character may also make its way in the game for five reasons:
-Toro's lvl 3 super in his caveman form imitates Akuma's raging demon
-Seth Killian joining the team
-Street Fighter 3 jumped onto Playstation consoles first after the dreamcast
-All Street Fighter Alpha and EX titles
-The exclusivity of Street Fighter x Tekken for PS3

Again, this is just my speculation but i could be definitely wrong

I was kinda thinking that SFxT might not be the last game featuring Toro, Cole, Heihachi and a Street Fighter. Would make a decent promotion. Plus Paul Gale's said that there's another fighting game character in the game, though most people seem to think it's Scorpion - he was hinted at, apparently.

I wouldn't like either one, really. Heihachi's okay, but having two fighting game characters seems like wasted potential, especially if really unique characters like Sir Daniel or Raziel don't make it in.

Sir Daniel is no exception. If i don't see him in All-Stars royale, then i say that its really wasted opportunity...
Raziel? Idk.. That was by crystal dynamics and Eidos so its a possibility.. Yet the kain series wasn't spoken of for a very long time.

Here are characters that may or definitely will make the cut:
-A street fighter character (i listed my reasons above. Im not expecting for one but i know its gonna happen)
-A soul calibur character (Mostly was on playstation consoles)
-Sir Daniel (No exceptions. PUT HIM IN!)
-Ratchet and Clank (Obviously)
-Solid Snake (Since Cole and Nathan Drake has been confirmed, its safe to say that the leaks from the voice actor definitely confirms this)
-Nariko (First leak)
-ICO character (Through an image leak)
-Sackboy (Has a level so it is possible)
-Crash bandicoot (Probably a big request from Sony fans)
-Spyro (Probably a big request from Sony fans)
-Gex the Gecko (Probably a big request from Sony fans)
-Dante (This also could definitely possible, seeing as Devil may cry was mostly a playstation exclusive)
-Kevin Butler (Rumored by alot)
-Spike or Spencer (C'mon.. You know there has to be an Ape Escape cameo in here)

Anyways, those are my guesses... Most of them are definitely wrong and thats for sure but thats my speculation xP

My opinion in bold. Plus I got the feeling a Final Fantasy character may be wormed in there somewhere. Probably Cloud Strife or Lightning.

I sort of don't want to see Snake in this... game. But hey.

I would like to see Lara Croft.

You know who would be awesome in this game? That guy from Legacy of Kain, its not gonna happen i know, but think of what he could do in this game.

Snake was hinted in one of Paul Gale's pictures; a Socom pistol outlined with bullets (Snake usually carries a socom pistol around).

I think it's pretty likely, based on the available information that there'll be a Metal Gear character. I thought Raiden would have a chance due to the new direction of the Metal Gear series (Lightning Bolt Action) but so far chances seem to be gearing towards Solid Snake mostly. Could be more of a matter of 'what version of Solid Snake' rather then 'could a Metal Gear character be in this game?'. I think Metal Gear deserves some recognition in Playstation's history, mainly because they pulled such amazing things out of the console's technology (RIP Psycho Mantis).

Sad part is that, right now, IF Snake actually gets in, no one will be suprised anymore. Kinda like 99% of the overal roster *cough*

EDIT: I feel talkative today;

What I really dislike about the roster is that just about half the cast is pointing guns at eachother right now. While I love Metal Gear Solid to death and back, I don't think Snake would feel very... unique in the game anymore. He was totally off the hook in Smash Bros. and DreamMix because Snake was the only one that relied on modern realistic weapons. Here, Snake would probably just feel like another brick in the wall. In my opinion.. at least.

Honestly I'm not surprised that half the roster are gunners. Half of Sony's games seem to be featured around modern and post-modern combat from what I've noticed. At least recently it has, anyways.

Anyone else hoping for Nariko?
Or do you guys think she's too similar to Kratos?

Nariko and Kratos are very obviously two different characters to me, but her inclusion doesn't feel like it would bring anything interesting.

Except for the obvious Twing Twang super. Thats going to be fun as hell.

Regarding a few of those choices:

-Nariko wasn't leaked, all we could see on that screen was a female model. Next to that model, notably, was a picture of Yorda from Ico, leading me to
-Ico, who I think is pretty unlikely. Having him and Yorda in the background of a stage would be nice, but if we get a Team Ico character, I'd hope it's Wander.
-If we got Dante, it would almost definitely be new Dante. Costume changes wouldn't fix his personality, either.
-One of the pics of the studio showed what looked like an Ape Escape stage, so you may be in luck there.

Beyond Crash and Spyro, everyone I was really hoping for is pretty much confirmed already. After that, I just hope the rest of the roster is more unique choices (Raziel, Sir Daniel, Gex, Kevin Butler) rather than wasted potential (Guy with a gun, martial artist from a fighting game, etc)

We're hard at work on polishing as we speak, and that of course includes the UI and SFX. The UI shown thus far is meant to be temporary, so you guys can expect to see a complete overhaul soon!

-Clock
Source: http://m.neogaf.com/showthread.php?t=471923&page=236

So it has been comfirmed that the current UI (selection screen, title screen, ect.) and the current meat slapping sfx are only temporary. I'm pretty sure it was kinda obvious but its good to see a comfirmation.

Also, possible new character sighting?

From left to right:
Kratos, Kat?, Drake, Sly


Quite a stretch, seeing as it's really hard to tell, but hey

And that stage looks like the Professor's lab from Ape Escape 1.

It'd be really cool if we could at least get Spike as a playable character, they could possibly use his specials from Pumped & Primed as his supers. And the Gadgets for his normal attacks.