They are definitely going to be in this game. They have a lot of history with Sony and the PS consoles. Tidus should be in it too. Honestly, I probably won't buy the game if it doesn't have one of these characters. This fact is solely because I do not know the other characters that well.
if we are to get a Sqeenix character,it will only be one, most likely. and that character would be Cloud, since he is the most popular character in the series and his game is one of the Founding series in the history of Playstation.