I'm pretty sure that both Microsoft and Sony are on a 10 year plan with both of those systems, which means you won't hear anything about a PS4 for another couple years at least.
That said, this seems like a pretty smart move on Nintendo's part. They get to release hardware thats not the most expensive/fastest available, but still beats the current market, and gets to live at the top of the performance chart for at least a few years.
From what I understand, the often quoted 10 year plan includes overlap with the release of the next console, similar to how the PS2 still sold quite well at the start of the PS3 era, as well as the PS1 before it.
The PS3 was announced about 18 months before availabiltiy, so we actually should be pretty close to an announcement.
The rational thing for Sony and Microsoft to do is to stand down on any new console. Both consoles push 1080p and there's been no mass adoption of 3D or other display technology to warrant a new introduction; Crysis 2 is being released for both platforms and there's no real consumer demand for yet more polygons. Both companies are able to turn profits on their gaming divisions; Nintendo isn't likely to outcompete them on a technical basis, either.
In short, I think the 10 year horizon might actually be too short.
Please no, both consoles have been holding back PC gaming. Crysis 2 actually has lower system requirements than the original Crysis precisely because they bent over backwards to make it work for PS3 and 360.
Actually it's about pushing the state of the art and the technology, something hardcore gamers have been the main driving force for in computing since the mid 90s.
But forget all that, you want to make money off of a Farmville clone.
Sony/MS said that Move/Kinect qualify as "a new console", which would put PS5/Xbox5 around 2015. I don't think they'll wait quite that long, but the next generation isn't coming soon either.
