I'm thinking 308 (though it could be a longer barrel 556 varmint/target setup). I'm a big fan of both the 308win caliber in semiauto rifles, as well as DD products. But for 308 I kinda prefer a Springer M1A or maybe even FAL. AR10's have tremendous potential, but there are a ton of compatability issues as well crazy costs involved in buying top quality.
But I'll keep an eye on it. Daniel Defense makes a great rifle.