The release of the new system isn't expected until 2014 at the earliest.
The PlayStation 3 is still alive and kicking, but that doesn't mean Sony can't have something else in the works. According to Develop Online, Sony has already assigned a few of its game studios to begin work on games for the PlayStation 4.
Though we've heard rumors of a new system before, the timeline does seem to line up with Sony's plans. At launch they said that they're looking for a 10 year lifespan out of the PS3 and a 2014 release would be right at the eight year mark.
Details, as you might imagine, are scant. Though it's been reported that Sony has given the job to at least one of its internal development studios, there are 16 to choose from and there's no word on which studio is handling the task. Don't expect anything official in the near future, but there's something on the horizon for sure.
Source: Develop Online