US Army Considers Adopting an Interim Battle Rifle in 7.62NATO: eventually adopt 6.5

[stanc]

The Marines are replacing the M249 with the Infantry Automatic Rifle (IAR). It is basically a M16 that is set up to be an automatic rifle.
That was my thought if they go to the 7.62x51, even temporarily. The M240 is just too heavy to carry as a squad rifle.

IMO, you may be right about the Army fielding an IAR version of the ICSR, similar to what was done to make an automatic rifle version of the M14.
First, I have seen no mention of a replacement for the M249, and it seems rather unlikely the squad would have 7.62 rifles and 5.56 squad autos.
Second, the program to develop an M249 replacement even shows the concept to be a magazine-fed automatic rifle, not a belt-fed machine gun.