I think you're right. And right at the end, they'd set another new release date. Suddenly, before that release date, they said "next Tuesday!" or something like that. It sounded to me like somebody higher up at Sony got very upset, and said "Do it now, by God."
But what were they doing for 5 years? Quite a bit -- that was a monumental project. From where we sit, it's hard to see all the tasks involved with porting all the cars over from GT4, the process development for premium cars, the issues involved with online racing, the restructuring/reprogramming of a physics engine...this is all very hard stuff.