What ault rifle will replace the M4/M16?

Ever since the US Military came out with the M16 ault rifle they have been trying to replace it. In the past few years we've had the HK416, Barrett M468 (REC7), XM8 (Now canceled) and a few others. The main compliant i think is jamming up, over heating, using too small of a round (5.56x45mm NATO), too long of a barrel. Rumor had it several years ago that the USSOCOM was going to have a special rifle built that was a modded M4 but fired the Russian 7.62x39mm due to that the round could be found next to everywhere. The Heckler and Koch 416 still uses the 5.56mm but has has a gas operated system like the Ak47. That gave it so it wouldnt have to be cleaned very often and it would last longer. Delta Force switched to the HK416. The Barrett REC7 is practically like the M4 but with a few differences and fires the 6.8 SPC round. The 6.8x43mm is the in between the 5.56 and the 7.62x51mm. The XM8 which was canceled mainly because the special plastic they built the gun out of melted after continuous fire. Which of the firearms will be the one that will completely replace the M4 and M16 rifles?