If you're being realistic with your worldwide hardware predictions the worst case for the Wii at this point in time is still much higher than the best case for the PS3 or XBox 360; this doesn't mean that it is impossible for the XBox 360 or PS3 to pass the Wii but it is very unlikely at this point in time.
I don't think anyone is foolish enough to be predicting a reversal in the market in 2008 so you have to consider the outcome of the Wii leading the market (by a wide margin) through out 2008. As of today, the XBox 360, PS3 and Wii have a similar number of announced third party games with intended 2008 release dates; when you factor in the quantity of games for the PS3 and XBox 360 that were delayed from 2007 (into 2008), and the very limited number of titles for 2008 release that were announced for the Wii a couple of months ago, it starts to become clear that the quantity of support for the Wii is growing (and is/may soon be much larger than than the PS3 or XBox 360). If the Wii continues to lead through 2008 it might end up with a dramatically better third party line-up in 2009 which will prevent any rapid comeback by the PS3 or XBox 360 in those years ...
Even if 2008 represents the peak of sales for the Wii, the lead that it will have built by the end of the year will take several years for the PS3 and XBox 360 to make up being that it will continue to sell at a decent rate until (at least) 2011 ...
