Either Sig sold the brass on this or the brass really did believe we need an infantry rifle that's capable of defeating Lvl IV armor. That would indicate there are concerns that we're close to a war with a nation state and not simple terrorist organizations, but when I hear that Yemen caused a US aircraft carrier to have to take evasive maneuvers causing a $60m fighter to fall overboard and sink to the bottom of the sea and Yemen launched missiles that defeated Israeli countermeasures and hit Ben Gurion airport, perhaps there is reason to be concerned that even Houthi rebels are something to be concerned about.
It's not 2001 anymore, the abilities of other nations, terror groups, drug cartels to make drones and equip their troops with body armor and nightvision is a real threat.
It's logical to want to prepare for that threat, but if in the future US forces are still dealing with poorly equipped enemies then slapping a rifle that weighs twice as much and reduces the ammo capacity an individual grunt can haul, then that's putting them at a disadvantage.
If the threat is serious (and I don't doubt it is in the long term) then we do need a rifle that is capable of defeating body armor that the 5.56 cannot and the .308 would struggle to. Was this XM7 the correct choice? Time will tell, but my opinion is that there is a need for both a rifle capable of defeating body armor and the M4/M16 for unarmored opponents and non frontline troops. The military will hate having to supply all the different ammunition for all the rifles, but we're at a point now that the troops need every advantage they can get because opposing forces are becoming more difficult to defeat.