Well, the 7 SAUM is a good round with factory brass, and look where it is. So you might be right about the 6.5 SAUM.
But if I was a betting man, I'd bet the Nosler will sell more, just trading on the name and people jumping on the long-range bandwagon combined with the novelty of the "best new cartridge."
I can see the Field and Stream fluff pieces now.
Keep in mind that as of now, the 26 Nosler is available in one rifle, and it's not cheap.
Rifle and component availability will affect long term cartridge life. There have been many, many cartridges go the way of the dodo due to limited introduction, wrong timing, poor marketing, or what have you. Not saying that will happen here, though.
