Let's see if they actually do show a Direct focused on 3rd parties. I concede right now things don't look especially good, but I suspect that at the very least Capcom and TecmoKoei are relatively on board.
Just of the top of my head:
Sega - I'm sure we'll see a couple of games like Sonic and Monkey Ball, but they seem to be focused on digital stuff and are contracting.
Konami -
Maybe we'll see a port of MGS or Castlevania, but they seem content on ignoring Nintendo platforms for the most part.
Capcom - They seem to be somewhat on board with Monster Hunter, but I have my doubts that they'll really make Resident Evil/Street Fighter a focus. I bet we'll see an Okami/lolMega Man exclusive at some point though.
Square Enix - I think we'll finally see a return of a mainline Final Fantasy game on a Nintendo platform. Dragon Quest is firmly on Nintendo platforms at this point, but Dragon Quest XI is likely for the 3DS. Anything like Sleeping Dogs though will probably not reach the Wii U.
Atlus - Seems like Nintendo has a pretty strong relationship with them. Shin Megami Tensei has become a Nintendo series, Persona 5 has a slight chance at a multiplatform release (although they might just see it as a Playstation exclusive).
Level 5 - I think their focus is on the 3DS. They'll throw Inazuma Eleven on, but I wouldn't expect too much. Maybe they'll throw a new IP on it, since they seem to be trying out new things nowadays.
Namco Bandai - Again, they seem like they have a decently strong relationship with Nintendo, so Tekken and a possible Tales game has a decent chance of appearing.