Nobade,
You have a clear head for figuring.... The wave of the future is hundreds of drones, some armed and some dummies, to draw Iron Dome response missiles. Just like before WWII, some nations were still building battleships when the aircraft carrier was clearly the wave of the future. A "new" infantry rifle in 2024 is akin to an "improved cavalry saddle" in WWII. Yes, a NEW saddle, but still strapped to a horse.
When I went into the service in 1962, less than half of the troops in my barracks ever fired a gun before. I suspect the number of recruits who ever fired a gun is less today. I see no need for the expense and quartermaster confusion for a NEW caliber. Most soldiers cannot shoot well, thus the Matel 16 "spray and pray" worked in the 1960s. It will continue on today considering marksmanship is marginal despite expensive optics, etc. A new caliber will not matter much in the next war in my opinion.
Italy in 1938 tried to change rifle calibers from 6.5MM to 7.35MM and finally gave up and went back to the 6.5.
Be well.
Adam