The only disadvantage I see to the cartridge is that the SAAMI specs do not leave much room for the bullet, so some long sleek bullets will not be usable. But the 300 Win Mag has the same issue, which has not hurt its popularity, and there are ways around the problem.
If the gun magazines have anything to do with it, the cartridge will be a wild success. They gush about it regularly, and with good reason. I have not read yet if the theoretical accuracy advantages are real, but it does sound like you do get less kick with the same velocity.
The waters might become somwhat muddied if Remington decides to come out with a similar cartridge, which I have heard is a possibility. It has certainly happened before (243Win/6mmRem, 270Win/280Rem, 338Win/8mmRem, etc. etc.). There being something else too similar, without any offsetting advantages, is what usually kills a caliber. Hopefully Remington will come out with a 7mm version and not a 300 with a slightly different case.