20 million end 2007 but with Halo3 GTAIV and a $189 Core in 2008, we could see 65 million by Xbox 720.
If Xbox 3 comes in 2011 that could be possible. As for a $189 Core in 2008... I would really hope MS would go with a SKU structure of $199 / $299 at their next price drop in 2007. It is going to be nearly 18 months between launch and first price drop. The first price drop sets the table for the gen as well as has the highest cost reductions. eDRAM to 55nm in late 2007; Xenon to 65nm in Q2; Xenos to 65nm sometime this year; GDDR3 700MHz is becoming quite popular and benefiting from economy of scale (e.g. not only GPUs are using it, but also the PS3 and Wii). Core has a cheap DVD and no HDD. With the eDRAM, GPU, and CPU all getting yield bumps per wafer in excess of 50%+ I expect a $199 Core price by the middle of summer 2007. But the money side of me says, "$229".
I guess it all depends on how much pressure MS feels they have from Wii and how big of a move Sony makes (who not only will be seeing the same reductions in RSX and Cell, but even bigger savings in BDR costs). I have no doubt Wii should be capable of dropping to $149, so having a console in the same impulse buy zone would be significant IMO. Further MS does not expect to break even in 2007 and I think strategically 2007 is MS's most important year. They need to strike now and follow up in 2008. If you look at Sony and their price drops their first one was a big one and then they didn't let up the gas every year.
Btw, kind of dissappointed not to hear anything about their FPS controller or hear anything from the White Fusion / Reflex guys