I seriously believe that Sony won't release their next console until 2014 and that it won't be a gimped console (ie. that it won't be as many people claim just an incremental upgrade over Wii U) but that like PS3 it will be more of a future proof console with more advanced tech under the hood.
What leads me to believe this? The fact that PS3 is still the Number One selling console in the world on a regular basis now almost every week. Sony's simply going to want to take advantage of that fact to get more of their exclusives into more homes and to begin to make more of a profit on PS3. However, the most important reason in my opinion that we won't see PS4 in stores in 2013 is that Sony's not going to release it until after the Playstation 3 has finally passed the Xbox 360 and in my estimation that won't happen until sometime in 2014.
Why don't I think the PS3 will only be an incremental leap over the Wii U ( in effect just 2 to 4 times more powerful as many say it has to be due to Sony's "desperate financial situation")? Because Sony is going to want to have the next games in series like "Uncharted", "The Last of Us", or "Beyond: Two Souls" look just as stunning compared to their PS3 iterations as PS3 games looked in comparison to PS2 games. That always seems to work out best for Sony in the long run ie. see how PS3 has become this console generation's best selling console at the end of the 7th gen. So, as far as power in comparison to Wii U, I really think that at the very least it will be comparable to the horsepower difference between Playstation Vita and the 3DS which some estimates say is about 10x that of the 3DS ( http://www.gizmag.com/playstation-vita-nintendo-ds-buyers-guide/22545/ ).
So for the reasons listed above as well as Jack Tretton's statement that Sony has never been first or the cheapest ( http://www.eurogamer.net/articles/2012-06-06-sony-on-ps4-weve-never-been-first-weve-never-been-cheapest-its-about-being-the-best) made at last year's E3, I'm not expecting PS4 to launch until the Holiday Season 2014.
I think Sony may learn a bit from their initial pricing of PS3 and that it won't cost $600 at launch; however, I still think you'll see PS4 be the very biggest beast that it can be for $500.00 at Christmas 2014 with a decent launch lineup posssibly including God of War 5 ( the one after Ascension), GT6, or Uncharted 4 as its launch title.