Sony is yet to confirm the existence of the PS4 games console, but it exists out there somewhere - you can be sure of that.
The latest rumours suggest that Sony is calling the PS4 'Orbis'. This comes from a source speaking to Kotaku "who is not authorised to talk publicly about next-gen hardware but has shared correct information" with them before.
Assuming the Orbis name is accurate, it's still unclear whether the name is a codename like Durango or whether the console will literally be called the Sony PlayStation Orbis instead of the Sony PS4.
The name does make some kind of sense if you combine it with the word 'Vitae' (or Vita). Orbis Vitae translates from Latin as 'circle of life' and hints at some serious synergy between the PS4 and the PS Vita.
It could be a red herring, of course, but with the Vita already communicating fairly competently with the PS3, it seems highly likely that this will be the case. So what can we expect from the PlayStation 4?

PS4 likely to pack AMD CPU and graphics power

The same source who revealed the PlayStation Orbis name also mentioned that the PS4 is currently penciled in as packing an AMD x64 CPU and 28nmAMD Southern Islands graphics power.
The source doesn't go into any detail about what revision of AMD CPU hardware it's going to be using, but it could be the forthcoming Piledriver revision of the weak Bulldozer architecture from the AMD FX-8150 CPU
Piledriver is also going to be used in the upcoming Trinity APU, which incorporate both CPU and GPU components on die, but the first iterations of that particular chip possibly wont come with the 28nm GPU part. Subsequent APUs are scheduled to include Southern Island components, so that is still a possibility.
Meanwhile, IGN reports that the PS4 will be powered specifically by the AMD Radeon HD 7670 chip and the A8-3850 APU.
If that's true, it really is a big surprise. Those chips aren't even the best that AMD currently has to offer - so by the time the PS4 goes on sale it would be woefully lacking in power compared to the latest AMD tech, let alone the most advanced chips from Nvidia and Intel.
By 2014, Intel will be shipping 14nm - or possibly even 11nm - CPUs and with that amount of transistors on a die, we're talking serious performance and efficiency gains..
So it's for this reason that we suspect - or hope - that early PS4 development kits may currently be using these AMD chips, but the final PS4 will most likely pack something a little more special. If that's not the case, it's time for hardcore gamers to start worrying.
According to the source of these rumours, Sony is attempting to get 4K gaming out the door with the PS4, along with full HD 1080p 3D gaming for the first time. We don't think it would even be possible to achieve this kind of output with the Southern Islands GPUs unless some kind of multi-GPU set-up is being used.
The Playstation 4 would also need to have some serious graphics memory inside it to cope with outputting to such high-resolution screens as 4K.
So we fully expect the launch specifications to be far more impressive.
There were actually some previous rumours that PS4 could use Nvidia's ARM-based Project Denver but this now seems quite unlikely.
It's far more probable that AMD is offering Sony and Microsoft (which is rumoured to also be using this AMD hardware in its XBox 720) heavily subsidised access to its CPU and GPU tech. AMD is currently being beaten by both Intel and Nvidia in the CPU and GPU markets, and so we reckon AMD needs these consoles almost as much as Sony and Microsoft do.

Backwards compatibility

When the original original PS3 unit shipped, it contained a chip that gave it the ability to play PS2 games. Subsequent iterations of hardware omitted this chip and so the backwards compatibility was condemned to death.
Current rumours suggests that the PS4 will completely ignore the possibility of backwards compatibility and focus firmly on the next generation. So if you want to continue playing your PS3 games, keep hold of your PS3s, kids.

Second hand games on the way out?

More rumours suggest that Sony is going in the same direction as Microsoft in that it wants to kill off the second hand games market. Current industry wisdom suggests that future PS4 games might be tied to your Sony Entertainment Network account and will thus then have no resale value. That's a similar approach as used by PC developers using Steam so we reckon this is a likely development. Doesn't mean we're happy about it, though.

What are the PS4 features we'd most like to see?

PS4info dreams of a next-gen PlayStation with a 32nm Cell processor an up to 16 SPEs, double the number in the PlayStation 3. While over on gamrConnect, there's talk of a greater partnership with Google. Sony's new fondness for Android on the Xperia Play is an interesting strategy.
Blu-ray on the PlayStation 4 is a dead cert. While digital distribution is undoubtedly the way forward, not every PlayStation owner has access to a fast broadband connection.

PS4 release date

Latest rumours suggest that the PS4 will launch in time for Christmas 2013, though Sony are remaining quiet on the issue.
VG247 is quoting an anonymous source (always a bad start to a rumour) as saying that Sony believes it is in a position to get the PS4 out of the door before the launch of Microsoft's Xbox 720.
We remember, of course, how Microsoft managed to launch the 360 a full year before the PS3 went on sale and that enabled it to gain a huge headstart, despite all sorts of technical faults and expensive repair bills.
So it's a no-brainer that Sony will be looking to make sure that doesn't happen this time. How it can be so sure of beating Microsoft to the punch is another matter though, and as usual we'd take these anonymous comments with a glass of salty water.
Meanwhile, if you side with the likes of ITProPortal, you might believe that "the whole concept of a single lounge-bound gaming device may become obsolete". The future of gaming may well lie in a more portable device/controller that you can play on the move or plug into your TV. .
Senior execs for a big US retailer told their shareholders that they don't expect the Xbox 720 and PlayStation 4 til 2014. That seems like a good guess to us, even though Sony has always said the PS3 will have a 10-year life cycle (which began in 2006).
Bethesda's Todd Howard, game director for the blockbuster Elder Scrolls V: Skyrim, also says that gamers should not expect follow-ups to the PS3 and Xbox 360 until 2014, at the very earliest.
Speaking to PSM3 magazine, the Bethesda exec said that gamers were happy with the current generation of console tech and that he didn't expect to see an Xbox 720 or a PS4 before 2014.
Long live PlayStation 3!