Call of Duty: Modern Warfare 2 "Juggernauts," anyone?

I think the ideal application would not be to load a grunt down with more kit, but to keep his original loadout constant and use the exoskeleton to increase his speed, range and endurance.

Oh, and if you haven't seen Raytheon & Sarcos' whack at exoskeleton design, check out this video. I'm not sure of its current project status (vid is from a couple years ago), but God have mercy on the enemy if they actually figure out a portable power source that can run this beast.
http://www.youtube.com/watch?v=Nhj3Z9o6t0g

Welp, no surprises here to me. U.S. Mil has been taking small arms manufacturers for a ride for a couple decades now, putting out programs and requests for M16/M4 replacement designs, and, for that matter, M9 replacements. Then they pull the rug out.

It has started to look like a grand version of the practical joke where everyone agrees to jump in a swimming pool at once. The industry can't afford not to jump first every time, lest they miss out on the contract of a lifetime. But, just as in the old gag, they end up getting soaked.

In terms of cost, you are absolutely right. However, the cost of infantry small arms in total is infinitesimal as a percentage of the whole equipment and operating costs of the U.S. Military. Even at retail prices, outfitting all service branches with a new service rifle would cost a few billion dollars, at the most - maybe half a percentage point of DOD's budget this year. And since we rely so heavily on infantry for the style of warfare being fought today, yet their unit cost is quite low in comparison to armor, aviation, etc., it seems difficult to argue the case against adopting a new caliber on the basis of cost alone. As we are currently at war, however, logistics concerns may indeed demand that we "stay the course" for the time being.

Whether infantry-intensive COIN is the style of warfare we ought to be fighting today or in the future, well, that is a whole other discussion!

Another question to kick around: Should the U.S. Mil. be looking for a new standard cartridge to bridge the considerable gap in range, power and weight between the 5.56x45mm and the 7.62x51mm? The 6.8 Remington SPC and other .280-ish calibers have been touted as possible compromises, lending a boost in energy over the 5.56x45 without conceding to the pitiful range of the 7.62x39mm.

Precision and tight tolerances do not have to yield sensitive functioning and poor reliability under adverse conditions. In my opinion, many Heckler & Koch firearms - among others - strongly support this case, some of which "Operator 594" listed in his original comment. For example, many G3 rifles and their derivatives possess DM or near-sniper grade accuracy out of the box, yet counter reliability issues with features like a fluted chamber and a recoil-operated cycling mechanism. The same goes for the Mk 23 SOCOM pistol, which possesses astounding reliability statistics alongside match-grade mechanical accuracy, triggers and sights. Maintenance requirements for these arms are average or easier than average. The main drawbacks with these particular examples are high unit cost and weight (and in the case of the G3 family, stiff recoil, especially when prone).