I don't think the 5.7 will ever gain popularity. It's a very niche round designed for armor penetration out of a Personal Defense Weapon (machine pistols and bull-pups). The only advantages are the ability to use existing variety of armor piercing .224 caliber bullets and reliability in full or semi-auto weapons.

.22-250 would be more versatile in a varmint rifle and 223 would also more than get the job done.