But the question is, just what can they put in next for the Chrono series? If Time and Space can be done already, perhaps anti matter?
The greatest thing about Chrono Cross scenario-wise is how Kato "upped the ante" by focusing on dimensional travel (whereas the audience was expecting a time travel redux).
There's a ton of different directions the Chrono series could go in --
Crimson Echoes showed that the morality of time travel was a subject left largely unexplored in Trigger, as well as the very real relationship between time travel and dimensional travel. Imagine making a decision in a past era and a future era's situation changes entirely due to the player's actions; heck yah. Chrono Trigger played with this a bit, but the concept could be taken way, way further. There's also the possibility of trying to outsmart a time traveling enemy, and moreover the possibility of a reboot for the series. Hey,
Batman did it, and that didn't turn out so bad, eh?