Rumor says that Playstation 4 should be launched in time for Christmas 2013.
Found on Digital Mojo is a page saying that Playstation intends to launch the next Playstation Console before the next Xbox console.
Let’s just hope this doesn’t leave Microsoft’s Xbox team rushing to to get a release out to compete with Sony Playstation.
also Noted here
Further reading says that the Xbox crew is working on two console releases. One is a lesser and should be released sooner than the next Playstation, but the full actual new Xbox release should be a short time after the Playstation 4.