One possible solution is having apps ship with 1x graphics with an optional download to have 2x. That solution, however, is not something I would like as a developer or as an user.

Over the next few years, we'll probably go back to having just two screen sizes (Retina iPhone + iPad). This is just a side effect of the transition to retina, and it will go away soon.

Though from Apple's perspective it would make more financial sense to have you go buy a 64GB iPad. :)