Soldier Systems has some photos of firearms at AUSA. You can see some interesting non-commercial rifles.
Knight's Armament LMG with M-LOK
SCAR has been hanging in the game and this version has a new lower.
SIG SAUER MCX in 7.62X39
The idea to have a carbine that shoots 7.62x39 is not new in MCX line but it does make it interesting when SCAR and some other manufacturers were developing firearms for the caliber as well. This one has a stock made for shooter wearing helmet and ballistic visor