The key to keeping it interesting is to have the latest tech as far as the release date is, but for the other side to use asymetric tactics such as human shields, IED's, propagada, suicide bombers, attacks on infrastructure, propagation of inter-tribal warfare. Now the question is how do you represent these things in a game, some can be done easily, others require more work on AI of the non-playable characters. So the enemy would grab for example a local civilian and use him a human shield. Then he can order an Al-Jazeera van to show how the US shouldn't attack a certain site. There would have to be some meter or point system on propaganda/world opinion.
Truck bombers, you don't know who's coming at you so you shoot indiscriminately. The enemy films when the US accidentally kills some civilians, but rightfully defends itself. Then the US can counter by deploying non-lethal weapons, we can show this footage and gain points on the world opinion meter. Obviously I'm not talking about how CM:SF would work, but just throwing out some ideas on how modern warfare can be more interesting then some might give it credit for.
As for more advanced tech, that would be part of the appeal of the game, it could be episodic with patches for some new technology. As loyal fans we might be willing to pay for the new tech to support the devs. Just my crazy rambling so you'll have to pardon me if it doesn't makes sense.