Nope, this can't be done. It's been talked about a couple of times. It's just not feasible given that the replacement display would have to have the same pinouts and signals, unless you were fabricating some kind of convertor.

And the real limitation is that the player software, which is why we all bought our Empegs, wouldn't support the higher resolution. So someone would have to re-write a custom player app, as well as hacking up the display drivers... I don't see it happening.