I guess a third DKC game from Retro would be pretty neat. It's not my preference, but Tropical Freeze was fantastic (Returns was solid too) so I wouldn't be disappointed with more of that.
Retro's been inching towards full 3D environments with every game, so I'd like to think a hypothetical DKCR3 would be fully 3D A-to-B platformer--think Mario 3D World, not DK64.