They have to keep all those legions of coders they hired to make FF13 busy. I mean what else are you going to spend you HR budget on, writers and game environment planners?


EDIT:
The existence of a new engine was originally revealed in a recruitment listing that used used iconic Final Fantasy 7 character, Cloud Strife's eyes, sparking yet another rumour of a remake.
Ahahahahaha

Thinking about it, maybe starting the next gen engine now isn't a bad idea. Not that I don't think launching your flagship title on a new console 4 years after it is released is an inopportune development cycle.