Aside from the obvious predictions (MH4/MM3D/New 3DS release date, amiibo wave 4, Captain Toad/Yoshi amiibo support etc), I'm gonna throw one other thing into the mix that I haven't seen mentioned yet:
Collectible Badge Catcher.
I think this has been available in Japan for about a month or so, and I'm surprised it still hasn't shown up in NA/EU. I don't even think a lot of gaffers are aware of its existence..?
This application is like crack. Pure Nintendo crack. It's a UFO catcher game where the prizes are collectible "badges" that function as decorative stickers on your HOME screen. There are all kinds of different sets available, from Animal Crossing to classic Mario, to Zelda ALBW, even Mario Kart. They also come with matching themes. (Unfortunately it costs money to play, but you get a chance of getting free plays every day)
Here's some examples of what you can do with them (yes there are even functional badges for the Settings, Streetpass Plaza, Activity Log, etc. icons)
I think they'll announce this in the Direct. Could even be a "It will be available to download right after the Direct ends" thing like they usually do.