For starters, the N900 successor could defeat its rivals if the already established N900 owners just shut the hell up with the complaints in this forum and actually contributed directly to Nokia.
App support to Nokia would have been a way to go as well, couple years ago at least. N-Gage was a failure and guess what the reason was? You cry for OVI Store and games, and when you actually had a working online store and service, you never bought a damn game.