I think the lawyers are guiding WotC and they're making a clear claim to their IP by releasing setting books for each of their settings.
Toril/Forgotten Realms,
Eberron,
Ravenloft,
Oerth/Greyhawk,
Athas/Dark Sun,
Krynn/Dragonlance,
Sigil/Planescape,
Blackmoor,
MtG planes,
Mystara...