Accurate SAUM mags are 2.95 long. Custom rifles with factory ammo will be a possible draw to it.SAMMI max coal is 2.955”, so not compatible with rem mag box.
I not aware of current factory rifles in 7 SAUM so the canibalizing would be in custom rifles. The availability of factory ammo definitely helps the 6.8s case, if it ever comes back in stock at least.
We all know marketing plays a huge role to really push a good cartridge. Because it fills a new niche for long range hunting cartridge. It can succeed if done right. Hornady makes it big but also gets detractors... the Western can be marketed successfully to the "anti-creedmoor" crowd.