Kain's Ex-Mode has been confirmed as Holy Dragoon and this scan showing Tifa in Dissidia Duodecim has been floating around (I don't know if it's real or not).

As for what I think of Dissidia Duodecim so far, Lightning is the only character that I'm okay with being in (I can't really say if I like her being in since I'm not that familiar with her). As for Kain, it makes me sick. The fanboyism that he gets is so bad, it makes Cloud and Sephiroth look like the most hated characters in all of Final Fantasy. At least those two had a lot of haters to balance out the fanboys, but Kain doesn't even have that. I was at least hoping that he'd be on Chaos' side so that he'd get trashed by the heroes in story mode, seeing how he's more of a villain in the original FFIV. Oh well, with his traitorous personality, maybe he'll be dumb enough to pick fights with his own allies and lose. There've been mentions of Kain randomly attacking Bartz when he didn't even do anything to Kain, so maybe we can skin him alive in Bartz' story mode. And I guess I can always let Kain join Sephiroth and Zidane in my list of characters I beat up in Dissidia on a regular basis.

...okay, now that I'm done letting off some steam from reading all of the Kain fanboyism on GamFAQs, I'll continue. If Tifa really is in, I guess it's a bit of a mixed bag. At least her fanboys aren't like Kain's who mindlessly trash talk all other characters that aren't Kain, and she is probably the most logical choice for a FFVII protagonist besides Cloud (though I was hoping more for Vincent since he has a better connection with Sephiroth). But the fact that a significant amount of people want her in because of her breasts is rather, bleh. I guess the addition that I like the best so far is the Emperor's Throne Room being a new level.