Springfield already has a solution, there is little reason to design a completely new weapon.
Actually there are a couple of really good reasons to do just that. Personally I lean towards a highly accurized version of the original AR-10 platform myself. This would accomplish several things.
First our guys would have the advantage of the heavier and more powerful 7.62 NATO cartridge thus extending their lethal range by a factor of nearly 2.
Secondly training time would be drastically reduced. All of the controls are placed identically to the current M16/M4 platform. Scout/sniper recruits are essentially 'pre-trained' on the platform. All they need to do is learn the ballistics of the heavier round.
Third they're not carrying something 'differen't on the battlefield. A weapon that looks identical to the M16 at first glance doesn't scream "I'm the sniper! SHOOT ME FIRST!" at the bad guys.
Then there's the weight differential between this rifle and the M4. Now I don't know if you've ever humped a 65 pound ruck around for days on end. I have and believe me you feel every frigging ounce. Anything that saves weight is a God send to leg, line infantry guys.
So that's 4 pretty good reasons IMO to look at a new weapon system for the 7.62 platform.
L