>>358554813
The low recoil combined with the 5 shot kill, and being $2300 makes it objectively superior to the AUG, and the M4 gets major value when it gets attachments, but the M16 doesn't need them. 
I agree that the AK dominates, but a one shot headshotting fully auto rifle will always dominate in the hands of a good player.

I don't think the M16 will replace the M4, but it'll definitely be used more given its much cheaper entry point.