Going by recent news, there'll be six storylines planned from after 'Elemental Evil' through to 2018. The second one of 2015 has an 'Alice in Wonderland' influence, and there's going to be one on giants. There's a chance of a Spelljammer storyline and I'd be very surprised if a Ravenloft one wasn't on the schedule.
Here's a mad speculation. 'Alice in Wonderland' is where psionics will be introduced. Yes, it's not necessarily an Underdark illithid stomper or a Dark Sun scenario (though it still could be!), but I can see Wizards wanting to try something different for psionics. When you think about it, Lewis Carroll's logic-bending universe is basically a whimsical version of the Far Realms. Also, it makes sense, given the number of psionics fans, to bring it in as early as possible.
Here's a mad speculation. 'Alice in Wonderland' is where psionics will be introduced. Yes, it's not necessarily an Underdark illithid stomper or a Dark Sun scenario (though it still could be!), but I can see Wizards wanting to try something different for psionics. When you think about it, Lewis Carroll's logic-bending universe is basically a whimsical version of the Far Realms. Also, it makes sense, given the number of psionics fans, to bring it in as early as possible.