Not entirely true...
The accuracy of today's 5.56 round is equal to that of a 7.62 nato.
On top of that, future weapons all seem to continue with the 5.56 configuration. The fact is that the 5.56 is more powerful and accurate than ever. Combine that, with a longer quality floating barrel in a bullpop design and you're set to go. The engagement range in a modern battlefield is getting increasingly shorter for infantry but for longer range engagements you need to supplement the 5.56 with i.e the above mentioned 417 or similar rifles.
The criteria for future assault rifles is, reliablity, light weight, accurate, fast target acquisition and engagement capability.
Your battlefield today is increasingly sophisticated with drones and sensors all over the place giving infantry less time in firefights before being engaged, meaning you want to find the enemy, hit him fast, and get the heck out. Furthermore, battles are moving into urban areas with more cover and less time to engage enemies before they "disappear", you would therefore want to put precise and accurate fire and hit the enemy unlike desert and open plain engagement which is more similar to shooting range or fair shooting, with plenty of time to aim and shoot.
I would personally equip my army with a 5.56 config, and back it up with a substantial amount of marksmen equipped with i.e 7.62 nato config rifles.
