At least on Amazon D&D 4th Ed is outselling Pathfinder. #1 spot this month is Divine Powers and D&D 4th Ed is the vast majority of the top 5, top 10, and top 20 of all gaming books sold by Amazon in the same time period.
I don't think that the point he's trying to make is "Pathfinder's outselling D&D". That simply won't happen. D&D has been the single biggest RPG out there, by a mile, for 3 decades. The point is that it looks like there's a significant-enough minority of D&D fans who aren't happy with 4E, to make something like Pathfinder a viable alternative.
Wasn't Hackmaster largely a similar response to those who didn't want to changevoer from 2nd to 3rd?
My experience across the D&D players I know is that 4e is seen as the better game while possibly being considered a different game thatn 3e was. Granted, we had several playtesters in our community and makes for a certain amount of player buy-in but, the players I played most frequently with find the improvements in overall balance to outweigh nearly an other improvemnts or flaws with the new game.