Sony has posted a somewhat mysterious message on their official blog teasing the announcement of something on February 20th at 6:00 PST. The page also includes this teaser video:
Could this the announcement of the PlayStation 4? It would certainly make sense with GDC happening a month later and it would give them a leg up on Microsoft who has yet to announce anything (or tease an announcement or tease the tease of an announcement). I guess we'll find out in a bit over 20 days.