Remington isn't chambering their R25 in the 260R and they spent a lot of time and money extensively modifying the 450 Bushmaster, including a very odd rim size, instead of going with the a shortened 300 Savage or 308ME (with a rimless modification). Like many other entities that grow too large to react well as conditions change, Remington isn't supporting a great product in their own 260R cartridge and they are reaching for the brass ring of marketing, instead of giving new life to a proven round, in the 300 Savage.
If Remington had really wanted a fatter case than the 300 Savage, a shortened 308ME-Rimless would be the answer to all their needs in their R-15 platform. It has almost exactly the same body diameter as their 30AR and could be trimmed .350" to give the same length. The two cases have the same 50,000psi ceiling. Even if the 30AR proves to be a world-beater (who are we kidding?) Remington probably won't realize it or give the cartridge the support it needs to succeed.
Duck, I know DPMS is building these for Remington and I could just dip one I bought from them, the way Remington does. I could buy a 12 pound AR in .260R, instead of the Encore I have which weighs just over 7lbs, however, I don't want to lug around almost twice as much weight and I'm definitely a one-shot kind of hunter. That's not to say I won't buy one, eventually, because I tend to think such a rifle, in that caliber, would be an exceptional choice for the one-gun survivalist looking for big-game and bad-guy stopping power. I don't think the 30AR will be as capable, at least not at the same ranges. For one thing, a 125gr .308 bullet does not have nearly the sectional density of a 140gr .264" bullet, when comparing like velocity between a 30AR and 260R.