As stated by a Sony Europe ad.
An advert in Metro (a newspaper) reads:
Now is the time. The world’s greatest players are going to entertain, create and amaze on the ultimate stage. This year a new
generation will push the boundaries of play and share in moments of wonder. This year players will become legends. PS4. Coming 2013.
Sony spoke to Edge and stated that:
We announced at the PlayStation Meeting event on Feb 20th that PS4 would be coming in 2013… the adverts are simply re-stating that message. More information about PS4 and all PlayStation Platforms will be announced at E3.
Previous rumors suggested that Xbox One would get a slight advantage over the PS4 as it was originally rumored to be released in the new year whereas the Xbox one was set for a Christmas launch. However this rumor seems to be untrue from this ad.
Source: Computer & Video Games