Both the 360 and PS3 will have to seriously flop over the coming 4-5 years for the Wii to have a chance of recreating the numbers the PS2 had....but one thing you are forgetting about? The lifespan of the Wii! Obviously Nintendo reckons that it will last until 2012 at least...but I have my reservations. That means they expect it to have a 6 year lifespan at least...I would sit it at 4-5 years in total with development in games slowing down come 2009.
Prediction (June 12th 2017)
Permanent pricedrop for both PS4 Slim and PS4 Pro in October.
PS4 Slim $249 (October 2017)
PS4 Pro $349 (October 2017)