CMMG was heavily endorsing the Mutant Mk47 at SHOT Show, with a very cool display and several of the rifles on hand. CMMG has said that the Mk47 has been well received (see TFB’s prior review here: http://www.thefirearmblog.com/blog/2014/11/30/review-new-cmmg-mk47-mutant/) and that they are planning “multiple calibers and configurations” of the mutant in the near future. I speculate that 5.45x39mm will be next (and probably dubbed the Mk74) as it would require very little modification of the Mk47 as-is, and the round is popular and cheap, but CMMG was tight-lipped about their plans. I would also not be surprised if a pistol version was introduced.
Keep watching TFB, as Phil will have more detailed news on CMMG’s AR line plans announced at SHOT.