The Marines are adopting the IAR27 for every marine which is a version of the hk416. It will be replacing all the Marines M4s& M16s, SAWs, designated marksman rifles giving every Marine the capability of all these roles but remains to be seen what they will do when the US Army switches ammunition as we all know you build the rifle for the round not thd other way.
We've seen the military go through with next generation rifle competitions before and decide not to to bother adopting the winner. Obviously wanted better than the Scar or ACR. Looked like they were going to adopt the HK416 which is used by SOCOM units like the French but have changed their minds.
The good news for us AR owners is that there will be a lot of military surplus 5.56 and M16/M4s as well as surplus rifles from other NATO countries.