This generation has changed the rules somewhat, but there's two reasons why this generation is going to drag needlessly on. The first is 'upgrading' your console like a computer. There was no way the Xbox 360 in it's original incarnation would have lasted 5 years; so it didn't. It was repackaged and slimmed down. The second is they made the choice themselves to make the console generation longer by building more expensive consoles; throwing in state of the art and top line technologies into a unit and selling the units for a loss.

Where does this leave Sony and Microsoft really? Yes they both have their motion sensing devices now, but neither are required purchases or built into the system; they are attachments. Nintendo had several years to show that motion sensing had some depth to it, and in the end it was a resounding "meh," and that's to a system in where motion sensing is part of the standard package. The Wii also the system that has twice the units out, so when it comes down to the game of numbers, they are not in Sony's or Microsoft's favor. Even with an impossible 100% motion sensing adoption rate on their parts, that still leaves them with half the pie, or 25% to them each roughly.

For them to 'follow' Nintendo's Strategy, they have to move units with motion sensing. So long as it's an option not a requirement it's not going to happen. At this stage of the game Nintendo will likely announce the development of it's next generation console next year, and possibly release it the year after that. Which is to say that Nintendo will likely further it's grip on the motion sensing part of the consumer base.

This is all a product of both Sony and Microsoft dismissing Nintendo as a competitor. They ignored what Nintendo had done for too long, and only reacted when the writing was on the wall with permanent ink. They committed a lot of resources into making this console generation as long as possible, and it's going to be difficult for them to shift the gears and get things moving properly when the next generation of consoles come around when Nintendo gets a 2-3 year head start on it's competitors.