The experience of Mini-30 and various ARs like LAR47 teaches us that design changes are required to accomodate the 7.62x39, or else the gun has to be stuck with a proprietary magazine. Even with one there are issues.
I have better hopes for 7.62x39 RDB. At least that design has an excess travel length on the bolt group, so it is possible for it to be reliable, even with AK magazines. But in reality, I don't expect much. Realstically, the best we can hope for is 6.8 SPC.