I'd open up the other most popular settings to be worked upon, this'll likely mean more Forgotten Realms, Planescape, Eberron and Ravenloft adventures for the time being. This'll likely begin in my first or second year.
I'd have Wizards focus on more setting material as well, in addition to putting out their excellent adventures. In doing this, I'd offer the original creators of those settings the design lead role. This'll likely begin in my second or third year. Ideally, these books would be similar to a GGtR or the upcoming Eberron book but more focused on specific areas and regions or races and cultures.
I'd also ensure the creation and playtesting of more classes and subclasses, enough to ensure that most of the class niches can be filled and also begin the creation and playtest of more of the niche classes and subclasses. This'll likely begin in my third or fourth year. I'd try to ensure books that are more player focused.
I'd then offer up the other popular settings, like Greyhawk, Dark Sun, Spelljammer et al to be worked upon in the form of adventures, and of course opening these settings up to the DMsGuild. This'll likely begin in my fourth or fifth year.
I'd also like to focus on other material, like another Lords of Madness, which was truly exemplary, or Libris Mortis or Heroes of Horror, or material like Magic of Incarnum or Tome of Magic or Book of Nine Swords. This'll likely begin in my fifth year. And ideally, these books would also be similar to a GGtR or the upcoming Eberron book but more focused on their specific niche.