I think there is a niche market of guys who really want that .450bush, 458soc, and .50beo, and there are a few folks in that group who have been disappointed by bolt failures in these monsters - or by the relatively lack luster performance compared to their case sizes; rifles which have to run outdated pressure standards lest they fail. How does a guy get around that? Build an AR-10 upper as short as an AR-15, build a round which fits AR-15 mags, and run the pressure up to AR-10(ish) levels... kinda the same mentality as the .450Marlin, which didn't do anything for the reloader the 1895 didn't do before; just a higher pressure cartridge so factory ammo could be high pressure without customer confusion... guys still build 458/450/50's, so this one standing tall above the rest, with better durability will be an interesting twist for the guys who like to say, "the Joneses try to keep up with ME!"
I think it's an easy market too - new cartridges in a bolt rifle are hard to sell, because it's all been done, and frankly, not many folks get worked up about bolt rifles. AR's are really all the same, so their buyers look for ANYTHING to stand them apart from the other AR's at the range... I still get guys every year asking me to build them .458socom or .450bushmaster... Mike Milli still sells his WSSM AR's and uppers, NEMO still sells Omen's... there's a huge market for the "I have the only one in the state" AR-15...
