Turns out Mitsuda is working on three projects: one which has been announced, a second with a "great creator," and a third which is still a secret. Any guesses? I can't find the original interview, but here is the report by Musica Ludi: http://musicaludi.fr/6934
Well, we know that Mitsuda's current focus is the Chrono Cross arranged album. That's project #1.
"Great creator"? Hopefully the creator in question is Tetsuya Takahashi, and the project in question is either the Wii U or 3DS game that Monolith Soft is currently developing. This would make the most sense since Mitsuda has worked on several Takahashi projects, and Takahashi is certainly someone who has been called a "great creator".
The "secret project" obviously could be anything. A game, anime, or perhaps a second Xenogears orchestral album.
Don't expect anything Chrono-related. Square is so self-absorbed with FFXIII spinoffs as well as a new action RPG (which is being developed by Product Development Division 1, therefore it will be terrible), there's really no chance.
Whatever the projects are, hopefully they will have a stronger Mitsuda presence. The last full-length RPG score he did (by himself) was Soma Bringer (a Takahashi production) and the Inazuma Eleven games (the third of which featured other composers, and the anime of which is now being taken over by a different composer).
Anyway, I'm trying to think of other upcoming high-profile RPGs. Konami is making Frontier Gate (with tri-Ace), and while the main town music is reminiscent of Mitsuda, it's not his work. There's also a new Suikoden DS game in the works, but that will surely be headed once again by Norikazu Miura and another fleet of freelance composers just like they did with Tierkreis.
There's also Level-5's many upcoming games. Time Travelers is an action game of some type and its producer is Akihiro Hino. Guild01 is a compilation of four games including an RPG by Yasumi Matsuno (although we're already pretty certain Hitoshi Sakimoto will be handling the music). There's also Girl's RPG, Fantasy Life, and a Gundam RPG (Mitsuda has done a few vocal themes for more recent entries in the franchise). Mitsuda, of course, was the driving force behind Inazuma Eleven's music for many years, so he obviously has a good working relationship with Level-5.