The Edge Magazinethat the PlayStation 4 will see a 2013 release in North America and Japan, but will be delayed til early 2014 in Europe.
The article also states that the PS4 will have 4GB of GDDR5 RAM (compared to the rumored 8GB DDR3 RAM of the Microsoft next-gen console.) It then claims that Sony will attempt to bump it to 8GB, allowing data speed of 176 gigabytes per second.
Various magazine techs are doubtful of the latter claim, but it remains to be seen. Sony will have aon the 20th February - stay tuned.