That's a pretty amazing number, though it's not quite a surprise when you consider it. First of all, Nintendo DS and PSP publishing takes a much larger investment than Apple's $100 developer fee and an SDK download. Second, while the DS and the PSP are certainly selling a lot of games, they're not actually releasing nearly as many as the hundreds of thousands of apps on the App Store. Finally, new DS and PSP games sell for $30 or $40, while new App Store games sell much closer to 99 cents. So the fact that there are lots more people moving to the much more open and accessible platform isn't really that surprising.
But a figure like that does show just how much Apple's handheld platform has changed the mobile gaming environment. I would argue that there's still a place for handhelds like the DS and PSP -- devices essentially meant to play games rather than check email or browse the Internet. Even with the iPad coming, Apple still isn't actually focusing on games, though the iPod touch is probably closest to that idea. Whether Apple focuses on gaming or not, there's no question that there's a huge new player in the mobile gaming space. Sooner rather than later, Nintendo and Sony may have to sweeten their deals to keep premium developers on their platform.