It is most definately NOT an ACR or ARX-160 in the game, it is 100% a XM8. Sorry, they might put one of these weapons in the game as well, who knows.
I am not 100% positive on the standard assault rifles for each faction, I am only making educated guesses.
The Dragunov is not confirmed at the least, just guessed there too.
I agree with others saying they shouldn't use an already-cancelled prototype weapon as the main weapon, but in the trailer it looked very popular among US forces.
Stay tuned because this list will be updated in the future.