Long life spans aren't a feature of Sony consoles, they're a feature of very succesful consoles. The PS1 and 2 were very succesful, but that's not really what's happening with the third. Total failure isn't the word I'd use either, but anyone can see the difference by now. Even Leo will hopefully shut up when he sees the release of GTA won't literally turn the charts upside-down. -_-
As for the Wii, it remains to be seen what will happen. A few months ago I made this estimate:
Scenario 1:
Nintendo releases a new console too early, third parties decide using the wiimote is too hard and keep making the same shooter over and over again, consumers suddenly start caring about HD graphics. Lifetime sales slightly under 100M.
This is the worst that can realistically happen at this point.
Scenario 2:
The Wii leads the next big leap in console generations (Atari->NES = SNES->PS1 = PS2->Wii). Third parties almost completely migrate over, cutting edge graphics lose most of their importance even in hype, and gaming becomes even more of a "normal" hobby. Wii sales around 150M.
Scenario 3:
Complete Nintendomination. Only a handful of practically second party developers are not completely Wii-exclusive, virtually every household has a Wii, even my dead grandmother gets ones, John Lucas elected President of the World. Wii sales 250M+
Back then I said the chances looked something like 20/60/20, but that was probably giving the high and low predictions too much credit. All that has really changed since then is that the low estimate is looking increasingly unlikely.
It'll be a lot easier to make long term predictions after we see the mid-term effect of GTA4 and MGS4 on PS3 sales, and hear what the development teams of those games are going to do next. So far truly excellent games on the PS3 have been few and far between, but far more common than announced new ones.