Huh? Not saying that I thought it would happen, but what do you mean not possible? PSP games look better on Vita than they do on PSP, and that has quadruple resolution. How's it not possible?
You would need to go the Apple route and push x4 the pixels (need to keep the same aspect ratio), which means that your graphics chips needs to perform better, which means less battery, which means more heat, which means more cost. Basically.
EDIT: also include high res graphics for each games, to support both resolutions.