They didn't announce Europe/USA release dates because GT Mobile.
Sony knows that, after the Japan March 2010 announcement, people in US/Europe are expecting the game to be released at the same time or even later as usually. So, when GT Mobile is released next week, its sales will be boosted due to lot of people would be wanting to grab some GT for the 6 month wait. And then, like 3 weeks after the GTMobile release, they announce Dec 2009 for Europe/US.
I say 3 weeks later because in one hand they need to give some space for the initial GT Mobile sales, on the other hand, they need to announce the 2009 GT5 release some weeks before it happens to start the massive PS3 sales as soon as they can before christmas. And as someone said, Japan has Final Fantasy by Xmas, Europe and US dont have a system seller.
And one last thing i noticed, 3 weeks after Gt Mobile release (1 October) is 22 October, the day before Forza 3 release. Wich could mean nothing.
Im waiting for US/Europe releases and ready for anything (good or bad).