Considering the past trend that saw Nintendo and Microsoft dump their old consoles once they launch new ones as opposed to Sony's continued support for older platforms I'd have to say the PS3 will likely have the longest lifespan.

The Wii it will follow the same pattern like the consoles in the past: NES, SNES, PS1 and PS2 like those before Wii is a market leader therefore it will be the one supported the longest.

the last one standing would be the Ps3, i dont think Sony will ever release a new console until they use the Ps3 to its fullist and that would take a lot of time , while the 360 would be second since games like gears already boosting the console to the limits , and the wii had/or will stop boosting pretty soon. they might need to think of a new Nintendo after a couple of years, but since the wii is getting alot of cash they might stick with it until they see otherwise.

The PS3. Sony's plan is to keep it out until it outsells the PS2. At this rate, that will happen sometime around 2056.

ps3

it has bluray format
still has many price cuts to go
untapped power
has past history

I doubt the Wii will actually be the last one standing.
If Nintendo is smart their next console will support all Wii title.
Nintendo makes a profit with every console they sell so once the Wii successor is out they do not need to keep supporting their old console, it's probably brings more profit to migrate users to the new one ( one reason the PS2 has been out for so long is PS2 hardware makes money, PS3 doesn't and PS3 can't play PS2 titles except some of the older PS3 SKUs).

Imma go w/ the PS3.. The parts will get cheeper, and it hasnt reached its full potential yet so PS3 it is

The Wii.

I'm amazed that so many people could look at the current market, sales trends and economy and come up with any other answer, but okay.

Lets see here. No other time in history has the last place console, or most powerful console techwise (Which incidentally, last place and strongest seem to go hand in hand) Ever lasted longer than the first place console. PS1 lasted longer than the N64, PS2 lasted longer than either the GC or the box, but this gen is going to be completely the reverse..interesting.