Close but not quite is my prediction:
Wii = 38 million.
360+ PS3 = 40 million.
Now those are numbers that do not defy rational logic.
Personally, I still believe the Wii is very capable of selling out production for 2008, although there is a good chance average shoppers will actually see them regularly stocked on shelves for the first time by Spring or Summer. Any excess production/inventory will simply be held over for the holiday season, which will most likely be sold through once again by year's end.
Broad prediction for the 360 in 2008: anywhere between 8-10million. 10-12 million for the PS3. Conservative estimate for the PS3, 360 sales pending the inevitable price drop. But without a doubt, beyond 15 million (which would yield a total of 40 million combined). 40 million combined is an extremely low projection by any estimate.
I'm not even going to touch generation total sales since those depend entirely upon how long each stays in production.
If Nintendo sees a significant drop in Wii sales due to higher adoption rates of HD displays and content over the next 2-3 years, I'd expect to see them use some of that revenue they're currently swimming in to finish development of an HD Wii that can render graphics at full 1080p. That would be the Wii 2.0, not a revised Wii with an HDMI port and upscaled graphics for current Wii games. In other words, entirely new hardware, new platform. If sales for the Wii stay consistent, expect it to have a long life for as long as this continues.
If 360 sales remain on rough parity with Xbox sales, they may end releasing Xbox 3.0 in 2010 (which is already being R&Ded, including soft dev kits), which would still be consistent with their claim that the 360 will have a longer life than the Xbox. Even if they keep the 360 in production in conjunction with an earlier release, that would still technically be consistent. But tell that to the inevitable POed Xboxers, particularly the ones who buy a 360 in late 2008 or 2009. If not and sales see acceptable growth, the 360 will enjoy a longer life.