The iPhone 4 jump to double the resolution was easy, since it has the same hardware as the iPad and the iPad has an even higher resolution. But you can't double the resolution so easily from the iPad, since that would result in a screen with more pixels then about 90% of all computers. And as you all know, you can't play many games smoothly at that resolution on any sort of average DESKTOP hardware.
For the games that it would be an issue, code it to run in a compatibility mode of 1024 X 768. There, problem solved.