prosfilaes
Adventurer
What genres WotC didn't cover in 3E, other OGL publishers pretty much filled in. However, campaign worlds I'd like to see done as official D&D worlds might include:
A Pirate Campaign: The world is a bunch of islands and the primary source of trade is via ship. Lost cities of gold, a tyrannical seaborne empire and vicious natives on monster-infested isles beckon adventurers with promises of profit and death.
I think there's always the question of whether to create new settings or add onto old. Paizo just finished their pirate Adventure Path and fleshed out part of Golarion for that. That brings support and familiarity; mentioning to the players that they've met a cleric of Desna from Cheliax means something to them, and you've got a list of Desna's holy days at hand. It also probably sells better; there's a lot of people out there who buy every book for Forgotten Realms or the Pathfinder Campaign Setting who would think twice about a new setting.