IGN has a small article up about the next Xbox generation and when it might be coming to living rooms everywhere.
I was just thinking about the state of the industry the other day and I truly believe, as stated in the piece, that this cycle will be longer than ever before- maybe a lot longer. I think it really all hinges on how long the recession that the country, or should I say world, is mired in will last.
If things hold the way they are or worsen into a depression, I think it would be safe to say that you won't see anything new for a long while. A global product launch, on the scale of something like a new platform, is just too big and way too important to allow it to fail or be held back in any way, especially if people just flat out don't have the cash to invest. I think the big three would most likely just wait out the troubles and plan for when the consumer might actually have that cash to spend.
Sony is saying it will be a ten year cycle for them- which would put the PS4's launch at 2016. Microsoft has given no such timetable, but who knows? With the way things are in the world right now anything's possible.
The bottom line is that you might want to just get comfortable with the idea that your 360, PS3, or Wii will be sitting under your TV for quite some time to come.