Too bad the 6.5 and/or 6.8 aren't anything more than a "closet round". That platform I think would be a good balance, between the two for a mass produced combat rifle.
Somehow the 5.56, has an entrenched mindset, and the .308, has been around a long time. Perhaps, in time there can be balancing point, to give the soldiers what they want, and the feasibility to mass produce it.