On display by Steyr at Eurosatory 2022 was an AUG series A3 chambered in .300 Blackout. This configuration has been available for military and law enforcement customers since 2019. According to a brand representative, there is a possibility that a semi auto commercial variant will hit the US market as early as 2023.
The primary differences in the A3 generation from past iterations are the change from the progressive semi to full auto trigger for a 3 position selector (likely reversible, with the safe position in the middle) and the addition of an external bolt hold open/release in the rear.
We would expect there to be some sort of gas system modification to accommodate the new cartridge. Rifles in the A3 series do include an adjustable gas regulator, so the AUG A3 in .300 Blackout will accommodate a suppressor without modification.
The barrel appears to be a full 16 inches. For reference, USSOCM fields the suppressed Sig MCX Rattler with a 5.5 inch barrel in the same cartridge. A full 16 inch barrel should only add about 400 Feet/second to the velocity over the 5.5 for most super sonic ammunition. While the longer barrel will increase the velocity, it will also be a bit quieter for the operator at the muzzle unsuppressed than a short barrel and actuate the bolt at a lower pressure. Sub sonic ammunition like Hornady 90gr Sub-X, the projectile will stay well under the speed of sound even with a 16” barrel.
The AUG in .300 Blackout is a cool sounding idea, but the longer barrel the bulpup platform requires will increase the weight compared to the Sig MCX Rattler. The main reason to adopt a full length bulpup in 300 blackout vs the short Rattler would be to take advantage of the reduced pressures and decreased noise. Other than the benefit of reduced pressures, I do not see much making this attractive for military contracts unless the customer is already widely fielding AUG rifles (such as Austria and Australia) . For commercial civilian sales, the cool factor should be enough to get them off the shelves once Steyr USA can bring them to market.