I'm not sure where you're getting your numbers that the iPhone will take over Windows mobile within another quarter. From what I've found, Apple currently has a 2.8% market share in terms of OS use on smartphones and Windows Mobile is up at 12%. Not to mention how far back they all are from Symbian with it's 57.1%.
He's talking about total MS phone vs iPhone sales next year, assuming that iPhone sales double and MS phones sales are flat. Which is pretty pie in the sky, imo. But having said that, I've not seen a windows mobile device I would give a second thought to buying.
http://en.wikipedia.org/wiki/Smartphone#Operating_systems