First of all this is not going to happen because WotC itself is not going to want this. They have very ambitious plans to release at least two D&D-based video games per year, and you cannot do that with just one studio making those games.
I think there is a way they can have two releases a year from a single studio. They need to embrace the adventure pack approach. Instead of making a new game, with new mechanics and features. Create a new adventure. Imagine as you start BG you see a screen that lets you pick which storyline you want to play. A single game engine could do MANY adventure packs. This would lower cost, speed up development and give players more of what they want.
They could then use other studios to take a different direction for other games. Such as a Skyrim style action adventure approach, or a strategy game approach.
The adventure pack to me is what would be the bread and butter. Use the base CRPG engine and then create a whole new adventure, maybe one set in Waterdeep, Neverwinter or even Athkatla. You could move off the Sword Coast and do something Cormyr, the Dalelands, Anauroch or any of the other places within the Realms. Even leave the realms and use other DnD based game worlds.
