is there gonna be a tenkaichi 4

If they don't announce it by the end of next year, then I wouldn't count on it :-). I really hope they do make one for the next gen consoles. There's still loads of stuff they can add to it to make the best DBZ game yet.

Maybe, maybe not - you see, they tapped themselves out.
When they start a new series, like Budokai, and then Budokai Tenkaichi, the only source material they have is from the series. One the game series has covered all the stories of DBZ, then their options run out. Every next game in that series would only be a remake of the last game in the series, get it? That's why Budokai turned into Budokai Tenkaichi.
But of course, since Atari is so damned cheap, instead of inventing something new and awesome, they regurgitated Budokai's gameplay system again in the new PS3 and PS2 games. They have different names, but they're just remakes (with minor improvements, graphics aside) of the last Budokai game.

They still haven't gone anywhere near an RPG. Screwed up big time with Sagas, and dare not venture into the beat 'em up category again, and won't touch the idea of a free roaming sandbox style Dragonball game.

The closest would be publishing Dragonball Online, but that's being worked on by another studio. They'll just end up taking the majority of the credit if it flies. If it fails, well, everybody knows Atari fails. No biggie for them.

well if they do it should be for both generation consoles, including the first xbox to give more people a chance to play this time, and to also incourage 4 player onscreen gameplay making fights more interesting, switching from tag to just an allout battle between teams,which would help story mode more true and multiplayer as a major upgrade while in story mode u begin from dragonball starting off as kid goku unlocking characters and playing their story from their orgins