In this market as soon as one of the "major" companies releases a system their competition is never that far; behind because none of them want to give any of their competition the opportunity to monopolize the market before they even bring their system to market. The reason we haven’t seen a system being released yet is that the Wii was far too successful for Nintendo to think about cutting its life short, and the first few years of the PS3 and Xbox 360 were so brutal that Sony and Microsoft want to prolong this generation to recover their losses.
With that said, I'm anticipating Nintendo releasing a new system in 2012 and I would expect that Sony and Microsoft would both release their next generation system before Christmas of 2013. By that time that Nintendo releases their next generation system, the XBox 360 will be 7 years old and producing a significantly more advanced system at a much lower price will be relatively easy; and, while Nintendo's system will (probably) be very powerful (compared to current generation systems) I would expect them to have their primary selling feature be something other than processing power.
