Out of the 3 next gen systems, I think Wii will die first, but not for a long time, because of the dated technology in it (excluding the remote) and lack of hardrive.
The firmware update is the main reason i feel this generation will be the longest we have ever seen. This is because the graphics no longer have a high need to improve, and new inovative features can get added to the system over time.
For example, If the gamecube had firmware updates, and added the wii remote and sensor bar using an update, it would not be much different from what the wii is now and so could have lasted 15 years. Things like wii fit have proved this, as it was not originally part of the system, but has been added on and sparked new interest in the system. Something like this can get added to all three systems at any time in their lifetime, which could hype the system up again.
