Either Bad Company 3 or WW2/Vietnam. Though I do see the possibilities with today's engines, I'm so f'in done with modern/future. A WW2 game on Frostbite would be incredible, imagine a full sized Normandy invasion with destruction and the graphic fidelity of Battlefront. Vietnam could fill the gap in between also, it's not modern yet it's still far enough in the past that it doesn't feel too overdone. And then there's Bad Company 3, I'd love to see the Russian invasion of the US finally realized in video game form (MW2 didn't do it for me) and finally finish the story.
Also I don't care what the game is, but each team needs their own weapons. Seeing Russian VDV running around with M4 carbines or Chinese type 95's really breaks the immersion for me. If you can unlock the other teams weapons at the higher levels that's okay, but it should really go back to the BF3 style of weapon selection