Two more confirmed characters: Vaan (FFXII), and Laguna (FFVIII).
Gotta say though, I'm not happy with how they're selecting characters to put in. In the original Dissidia, it was the main hero from each game and their main villain counterparts. It was pretty much unbiased, with the exception of adding Jecht in over Seymour. With 012 though, it feels like they're just putting in their favorite characters now. Perhaps its just me, but Seifer would have made a much better choice than Laguna, due to not only having a bigger role in the story, but having a more understandable battle set-up compared to Laguna's machine gun. They also openly stated that they wouldn't even make the game if they couldn't add in Tifa (and we all know why Square Enix loves her), and are adding in extra characters before even deciding on the villain counterparts for FFXI or FFXIII. They were considering dropping Vaan altogether originally, due to voice actor issues.
Willing to bet right now that Auron from FFX gets added in because of how popular he is for Square.