Sony is going to release a follow-up to the hugely successful PlayStation 3, but we remain in the dark about when this will happen.

The latest reports suggest that Sony will launch the PS4, codenamed the Orbis, in time for Christmas 2013 but so far very little is known about the next-gen console.

According to a report from gaming website Kotaku, a prototype of the console is already being shipped to select developers and we will be seeing it launched in-store in 18 months' time. However we are likely to see Sony unveil it first at games trade show E3 in June 2013.

Some of the details which have been leaked about the new console relate to the graphical power inside. According to sources speaking to Kotaku, the PS4 will feature an AMD x64 CPU combined with an AMD Southern Islands GPU which will allow it to push games at resolutions of 4096 x 2160, making it future-proof in terms of televisions sets in coming years.

The Southern Islands GPU will also be capable of playing 3D games in 1080p (the PS3 could only safely manage 3D at 720p).

In terms of software, sources claim the PS4 won't be able to play current PS3 games, or indeed used PS4 games unless the user pays a fee to Sony. This is an attempt to cash in on the growing second-hand market by Sony.

Whatever about rumoured specs, we know even less about the look of the new PS4 but that has not stopped some creative people from coming up with concept designs for the PlayStation 4, which range from the sublime to the ridiculous. Here are our top five concepts.