Since AC3 is based on the rivalry between two mega corporations, I think the next ace combat will be on the rise of Neucom Inc and General Ressource ltd. Since the R-352 is the first starfighter ace combat (first appearance in AC3), I think there will be missions in the stratosphere instead of space missions in the next ace combat.
The problem is that we need a Game that explain why the space elevator wasnt at 2030 and why the two corporations didnt cared. It should happen somes years after lighthouse war because if It comes down so fast It would be remembered as the higgest fail in the history but It should take place at least four years before AC3 to allow people to asimilate It and not to Talk about It ever they heard "space". So we have to prepare to another war at Erusea before go to space with our macross' friends