In any case, the XM-8 appears very conventional in design, if one simply removes all the electronic geegaws. it's still a gas-operated automatic magazine-fed rifle, just more robust and reliable than its predecessor. Don't forget, polymer won't decay in a wet, humid environment like the M16's aluminum would.
In a jungle fight if you're calling in air support , then you're probably already screwed. Later versions of the M16 were pretty reliable as long as it was kept fairly well maintained. It 's easy to jump on the bandwagon for something new. We could end up trading a good rifle for something less that looks good.