The last 2 US service rifles didn't do too well out the block. The M14 being so bad it got binned quite quickly whereas the M16 went on to one of the best weapon platforms out there. The M7 will mostly likely be adapted however unlike the previous 2 it's not just a replacement weapon. You have integrated optics, 3 bullet variations with the high powered version able to penetrate level 3a/4 at 800 yards and it's suppressed to reduce the noise signature making it harder to pin point your fire position.
The next war being planned is most likely China who's troops will be armed with body armour. The previous conflicts using 556 proved that 556 just annoys the bad guys when they are high on drugs, plus they fired from stand off positions making the 556 ineffective at range. The M7 with the high powered cartridge will overcome the body armour and lethality at ranges unseen on a modern general issue weapon.
On the topic of drones this problem will likely be solved during the Ukraine war. At a guess using electronic counter measures and the drones greatest strength is also it's biggest weakness. The ability to see your target and drive straight into it has been a game changer over traditional artillery (and the Ukrainians use the drone because they have limited artillery shells) however if you stop a drone from seeing then it's just another artillery shell. Once someone figures out how to blind a drone the threat will be reduced. If you think that this doesn't apply to fibre drone then I'm talking about the camera on the drone itself not the drone feedback to the operator and with the drone blind AI would be useless as well apart from predictive targeting based on the last known image
Going back to the M7 and the 6.8mm round this will probably become the new NATO round simply because the US dictate which round is the NATO round. The fact that the British are looking to replace the SA80 with something in the 6.5 or 6.5 calibre suggests that moves are afoot to make the 6.8 the new NATO round. The 6.5 is probably a red herring (a bit like the EM1, good idea but shelved because the US wanted 7.62). I hope we don't try to make something ourselves as we have lost that skill and the skill fade is even bigger since we designed the SA80. It's probably best to go to someone who knows what they are doing (HK, SIG, LMT, etc) and just license build them in the UK.