That's an excellent question. I think that much of the theory generation has succumbed to the need to develop COIN tactics, techniques, and procedures that can be employed by infantry.

Some of the other longer trigger puller threads we have here about organization and platoon weapons will show that much of the discussion goes back to things of old.

Perhaps there can be no more new theory . Well...in the Marine Corps we've got something about distributed operations, but that cannot be bumper stickered to just the infantry...I think. And I don't think that the concept is especially ingenious. Lately, it has become a boilerplate for technical solutions and justifications for particular gear sets (or at least that is my impression).