If it were a problem like that, you wouldn't hear about in a press release. You wouldn't hear about it at all. Problems do indeed happen in that part of the process, but it'd never, ever warrant a press release. Certainly not with "indefinite" chucked in there.
It reeks of a marketing/financial decision tbh. You don't play all your cards at once, and with FFXIII set to be released in March, and with sustained and pretty good unit sales for the last several months for Sony, they'll want to split the aim of the PS3 sales in to two categories. Those who will buy it for FFXIII and those who will buy it for GT5, you release them the same time, and your console sales will not be as good as they could be.
Also worth noting how close between the box-art being delivered and this delay being announced. Still, it's not going to be much more than a month or two.
I don't see what FFXIII has anything to do with it. It was released in December in Japan and GT5 was to be released in March. If you're referring to the NA FFXIII release in March then I still don't follow the argument, since GT5 was only going to be released in Japan in March, not in the NA. They don't care about people importing the game. It's such a small percentage. Heck, I'm hard pressed to think that the majority on GTP is going to import it.
The reason why it's delayed, is naturally because it's not finished yet. Or rather, KY can't make up his mind if he's done with the game yet. I still think the March release was fake from the very beginning. It seems like Sony Japan was fed up with him and just announced a date and he had to go along with it.
Really, it's the same story with every GT game. The give him a deadline, he usually don't make it and then he starts cutting out features he planned and finally wraps it up.