What comes next is anyone's guess, but I have a feeling this will go one of a few ways:
- Wizards will follow up with the secondary core set of 3.5 and move on from there with the various core setting books for the 3.5 edition (Forgotten Realms, Eberron, ETC).
- Wizards will finally release the d20 Modern books to wide release through OBS and may even include some of those long sought after "proofs" that never made it to the public (I'm looking at you d20 Supers!)
- Finally, what I think is most likely, is that Wizards will move on to a slow release of another edition of the game ... my bet would be 2e.
Wizards seems committed to correcting the mistakes of its past and fully embracing the online media culture of the 21st century in such a way that seems almost natural and not as negative to its pre-existing fan base (I'm looking at you 4e spot light videos!)