Sony unveiled some details about their coming PlayStation 4 such as a whopping 8GB of GDDR5 RAM, a switch to an x86 processor architecture instead of their PowerPC Cell architecture (basically it's like your computer now), this interesting new controller which does too much (just how I like it), a new PlayStation Eye camera, the ability to stream PS1, 2 and 3 games from a cloud service (their excuse for no backwards compatibility), the ability to play a game before you download it and the ability to share live video of any game you're playing and some advanced new remote play stuff.
_{Still no mention of cost or release date though, nor have they shown much of the system software.}
(Source: PlayStation Europe Blog)