Final Fantasy XIII-2's producer and director has hinted at a new project, leading to speculation that it may very well be Final Fantasy XIII-3.
The Final Fantasy XIII-2 Ultimania Omega book was recently released within Japan. In it, a fresh interview with Yoshinori Kitase and Motomu Toriyama saw the pair suggesting (via Gematsu) a successor to Final Fantasy XIII-2 could come into fruition.
Firstly, series' producer Kitase stated (possible spoilers ahoy):
(The last part about Lightning’s DLC Episode) Explaining “XXX Years Later” would be pointless. It might seem that the line “To Be Continued…” means that Lightning’s chapter will continue in more download content, but we are doing it in a different interpretation.
Toriyama, meanwhile, teased:
With Lightning remaining in the ã€‡ã€‡ã€‡ã€‡ãƒ« (crystal?) but still keeping her heart, you could say that the world of Final Fantasy XIII will be permanently ã€‡ã€‡ed. I’m praying for the day to come that Lightning will surely ã€‡ã€‡ã‚ã¦ (wake up?) and Serah will be rewarded. Like Lightning advancing one step forward in the secret event, I think we want to take a step forward to advance our own project. From now on, I’d be happy if you could anticipate it.
The domain for Final Fantasy XIII-3 has already been registered, as well as "XIII-3" itself being trademarked. Square Enix has stressed that they only carried it out for "trademark purposes". Either way, Final Fantasy XIII-3 couldn't have been trademarked by anyone else but Square Enix due to the "Final Fantasy" name being included.
Furthermore, many have suggested that Final Fantasy XIII-2's ending leaves a slew of unanswered questions, which is too vast to simply release in a downloadable content pack capacity. The sequel itself to the first current generation Final Fantasy title sold 524,000 units during its launch week in Japan. That figure reached 1.1 million copies worldwide during March, 2012. That said, week-one sales of the game were just a third of its predecessor. But, who are we to question Square Enix's milking of franchises?