Well, they're doing more than your typical eight hour game release though.
They built an engine, which can of course be time consuming. Especially if they started from scratch.
Games typically spend about a year in pre-production which is just talking and planning and art; nailing down a vision and major goals. For a game as typically lengthy and as full of content as Persona, I could see them easily eclipsing that typical time.
Then there's the fact EP and P3 are seperated by six years. New engine, new platform; they're in that situation again.
I don't think it's releasing any later than 2014. But it's definitely not a quick production.