As far as what’s coming, WotC watches sales on DMsGuild. So one way to influence WotC is buy stuff there. For instance they plan on supporting Eberron with adventures on the DMsGuild. Want more settings or more Eberron? Buy them.
I expect to see the following books in the next year or two, but in no particular order.
1. Remake of old Adventures compendium: Greyhawk, Planes, or based in less common regions.
2. DM side book: Mass warfare, vehicles, stronghold building, monsters, more Planes info.
3. Player Side Book: I think this one is going to be a compendium of other Forgotten Realms regions much like SCAG, with subclasses. It could be a Planes book, but I think it might be Kara-tur and Zakhara.
4. Adventure Book: Based on the new subclasses and what hasn't been covered in an adventure yet... I think its going to be a Great Old One style adventure in the Sea of Fallen Stars region. Im also seeing more Feywild stuff lately, so maybe Star Elves of Aglarond and the Abolethic Sovereignty?