It seems that Square Enix is being quite the tease. Details of the Final Fantasy Dissidia character roster are being revealed little by little, and this time it's been confirmed that Final Fantasy X's Tidus will be featured in Square Enix's battle game.

As the main protagonist of Final Fantasy X, Tidus bid his companions farewell at the end of the game, only to resurface in the sequel and in other Square Enix games like Kingdom Hearts and Itadaki Street Special.
Here's a video of the Game:

http://youtube.com/watch?v=B_9ZYoM9cao