I was talking with my brother earlier, and thought of a cool idea for BF4, though they almost certainly will just make it just like more BF2/BF3 style.
We thought it would be cool to see the first major FPS war title that truly had a variety of eras to play in. WW1 (horses! maxim guns! gas!), WW2, Korea/Vietnam, Modern. It could open up some awesome and hilarious game modes. You could have mixed mode maps where you could get achievements by getting kills with really antiquated weaponry. Seeing a P51 trying to shoot an Apache down would also be utterly epic. Personally I'm tired of the modern warfare style shooters at the moment, we've had a big rush of them similar to the WW2 glut of the early 00s. As a matter of fact, it's probably time to go back and do WW2 with the new horsepower of the current engines and gpus. After seeing the aftermath maps, I think the rubble/grit of destroyed European cities could be really intense to fight in.
/all dreams though. I have full expectations that BF4 will be indistinguishable from BF3, though it's possible they could try to further consolize it with CoD dumbassery. I want my BAR, I want to drive a Tiger, I want to fly a Zero, I want to try out a STG-44, etc. And the best thing : no freaking heli or jet spam, lol.