I think it's important for us to not to get too caught up with the 10MB network limit or the app sizes. If we look to the very near future, that 10MB limit will most certainly increase, either this year or the next, as cell networks are upgraded to LTE. And flash memory in these devices will quickly multiply too. So I believe the ultimate answer will be to have a universal app for both devices. The larger size *could* be an issue for some users, depending on the game. I do like Anders idea to get around that in the mean time, but if Apple doesn't implement that, it may just mean users need to be more proactive about organizing what content to keep on their iphone/ipod touch at any one time. I don't like the idea of separate apps for the separate devices, or upgrading to an iPad version over DLC. Mainly because I know a lot of non-tech owners won't have a clue about doing that and will likely just run the app in 4x mode.
Being under 10MB earns many devs a lot of money every day. None of us trust ATT to change a thing anytime soon. For me personally, it's the difference between paying the bills, and not paying them.
Forget the download limits, there are a lot of 8gb device owners who will lose out if every major app doubles in size because of graphic data they will never see!