Sony confirmed again early December that they are on track to launch the Playstation 3 in Spring 2006. The Sony PSP did launch in Spring 2005 in the US. Sales where ok, but it was not great either. The PSP was already on the market in Japan in December 2004. The Sony PS2 launched in Spring 2000 in Japan. The US launch date was in October 2000.
I predict it will be the same with the PS3, because the global launch of Microsoft did not bring any advantage in my mind.
On the one hand you have still tons of disappointed consumers in the United States who wanted an Xbox 360 and did not get one. In Japan the Xbox 360 sales numbers did disappoint. Europe is in between. If Microsoft would have focused on the US first, it might have been better.
Sony can start selling the PS3 in Japan in the middle of Summer and it would still be a huge success. For the US and Europe the main season to launch a video game console is autumn. There is no way around that. Every other launch time would mean a soft launch.