from PSM:

"Back at E3, Namco revealed that they were working on a new Tekken game
for PS3. While it would seem pretty much a given that this would be
Tekken 6, I've also heard through the developer grapevine that it will,
in fact, be a PS3-only-follow-up to Tekken Tag Tournament and will
launch alongside the system in Japan and the U.S. We'll definitely keep
you keyed in as we hear more!"