Actually, I wouldn't be surprised if at least one Triceraton Warrior (prolly a generic) made it in game. The Trikes are long-running characters that have appeared in the original Mirage comics, as well as both cartoon series, and a few game appearances here and there. Peter Laird himself has a special spot for the characters. In fact, as far as original concepts go, the Trikes were actually crafted BEFORE the turtles themselves.
So, all that to say, I think a Triceraton is to be expected, as well as Usagi. Usagi's been rolling with the Turtles for years now, (crossovers in his series, as well as the TMNT's own) and I couldn't imagine him missing out a thing like this. Hell, I think it's safe to presume that most people don't even know that Miyamoto Usagi is actually a character from a separate series altogether.
No Turtle fan forgets Aska. ^^;
While I could stand to see Aska, in the end, she was a concept (created by Konami) that was crafted for only that one game, and hasn't been seen since.
Asking for her would be like asking for such characters like Tora the Bad Ass Polar Bear (TMNT2-NES) and/or Sisyphus the Beetle (TMNT Tourney Fighters, GEN/MD). Love 'em, but only the most hardcore of the hardcore TMNT fan would remember them, and we can only be but so marketed to by these guys.
Besides, if it came down to it, I like Aska, but plenty of the females that have appeared in the TMNT multiverse, like Karai, Renet the Timestress, Radical, Lotus Blossom (80s toon), or even Ninjara would be more deserving of that spot, in my eyes. Especially Renet.
