Colt451911,
I too would dearly love to see our troops better armed with a service rifle/caliber.
I've met met and interacted with several hundreds of these fine young men in my work, and they are universally armed with the M4, M16A2, and M249 SAW individual weapons. The troops like the M4 for it's handiness in armoured vehicle operations. As long as we and our NATO allies are stuck with the 5.56x45 caliber, the M16A2/M4 platform is as handy and effective as any other, including the "bullpup" designs.
As for caliber effectiveness, the Israeli and the South African Armies have more than a generation of continuous infantry battle experience using 5.56 weapons. They consider it superior to the 7.62 NATO and 7.62x39 ComBloc weapons, and they (the Israeli Defense Forces in particular), had a lot more armoured vehicle battle experience than the US Army until the recent Iraq conflict.
Given that the decision makers in US military weapons procurement still think that the troops have a "serviceable" weapon in an "adequate" caliber, it's much more likely that ammunition improvements will happen before weapon mods and caliber changes. Remember, the weenies that make weapons purchasing decisions think that "good enough" wins out over "best quality" every time.
HTH
John