And since when has the US Army been behind the curve? It's been nearly one-hundred years.
When we forced 7.62x51 on NATO as the standard service rifle round we were about two decades behind the power curve.
I wouldn't hold your breath, as rcmodel said. It might become popular with SOCOM types but isn't likely to become general issue.
Just about everything else SOCOM does gets lapped up by Big Army like a crackhead on vacation in a Colombian coke lab (though sometimes in watered-down, senior officer/sergeant major "fixed" form . . .). Once SCAR is fully up and running in SOCOM it will have a real solid inside track to replace the M4/M16 -- existing logistics track, trained armorers, etc etc, plus that magical catnip for decision makers of "as used by ninjas who're way better than you ever were."
HK, Colt, and everyone else with a dog in the fight will spend the gross national product of Sweden in lawyers fighting that process, of course, so we'll see what happens. Personally I'm with the "ain't broke, why fix it?" school of thought on the 16/4, especially since Congress, in a rare moment of lucidity, seems to be getting ready to make the army ditch the Universally Ineffective Camouflage Pattern ACUs some idiot general foisted on us, which is only going to cost millions and millions to fix all the assorted junk they put that bizarrely ineffective silliness on.
Think about it. What do Britain, France, Israel, Australia, Iran, and China all have in common with their armed forces? They've switched to a bullpup. Even the Germans are looking over some designs. Given the close-combat the Army has seen in Iraq, and the distances fought at in Afghanistan, the military needs a weapon that is both compact and maintains the muzzle-velocity you see on 300+ meters weapons. Only a bullpup rifle can give you that.
I'm pretty decent but not world class running an M4, and am willing to bet I can beat the best those countries have to offer when it comes to actually running a gun -- not just poking paper across manicured lawns, but shooting on the move, changing mags, and making hits at real combat ranges. Bullpups give you longer barrels and take away speed and situational awareness when it comes time to change magazines, etc.
Doesn't mean the bullpup is the wrong answer, just means it is definitely not a consequence/minus free option. Until we can move past the cased cartridge to something superior we're mostly just tweaking things and picking which set of advantages and disadvantages we want to accept.
If they do replace the M16; will the M16s become available through CMP?? (in neutered form, of course)
Nope. As was mentioned, once a machinegun always a machinegun. The government could possibly surplus out uppers or something, but I agree that they're more likely to find their way to Iraqi, Afghan, and various other friendly foreign nations' hands.
