Giving up 7.62 for 6.5 would be a mistake, going to complete 6.5 across the board would be an even bigger mistake.
I actually think the adoption of the 7.62 NATO was one of the biggest blunders we ever made, and then forced on England and our other NATO allies. The .30 bore is so Great War-era.
The question you might be asking is, "Well then what do you propose to answer the 7.62x54R with?"
A 130gr 6.5mm starting at a modest 2650fps from belt-feds and DMC's. To match its exterior ballistics with the 7.62x54R, you need to use the 7N1 152gr Sniper load at 2700fps, if you accept and believe the advertised BC for the 7N1 of .498 for G1. For comparison sakes, the new Berger Match Target Hybrid 155gr has a G1 BC of .483, so the Russians' sniper copper-washed steel bullet must be world-class, but that's another topic.
The 130gr class 6.5mm pills range from .485 to .551 easily. Then look at penetration:
Sectional density is king, especially in armor penetration, and the 6.5mm projos have over a century of excellent penetration on-record. Add to that the ability to carry 30% more ammo per weight, in smaller bulk, with half the recoil of 7.62 NATO, and you're talking about seriously enhancing the soldier's ability to shoot, move quickly, and sustain the fight with a terminally viable projectile weight.
Believe me, I've humped my share of 7.62 NATO, and love its downrange performance, but it was an albatross hung on the necks of infantrymen by bureaucrats in the Army Ordnance Corps who pushed their inferior universal caliber rifle/machine gun concept onto the Infantry board with the M14/M60.
The Brits had a much better cartridge with the work they had been doing with 7mm. If the AR10 had been built around the British cartidge concepts in the 1950's, it would have been the best route to take over the 7.62 NATO. The FAL was originally chambered in 7.92x33 Kurz, then in .280 Enfield, then got up-sized beyond its initial design parameters to feed on a yesteryear battle rifle cartridge that you simply can't sustain the fight with, which is why the M14 was so short-lived, aside from all its other failure points.
To my friends in the UK: Imagine a lightweight AR chambered in something like the .280 Enfield, only lighter, with better BC's and less recoil.