Only time will tell if it's a viable open shotgun but it's looking good so far. It has a few advantages over the Saiga mainly due to how much easier it is to get them running out of the box, last round bolt hold open and available factory replacement parts. They also have AR ergonomics so manufacturers don't have to spend a lot of time cutting/welding/changing everything over to to work like an AR....this leads to the lower price.
Firebird and Tromix are producing 922r compliance parts so right now the biggest problem is the magazines. You're pretty much limited to adding extentions to the factory mags. Things are moving ahead a lot faster than with the Saiga since the shotgun aftermarket is already in place. Id say give it a year or so and all of the parts should be readily avaiIable for the home builder to put one together for 3gun.
I don't think everyone is going to be throwing out their tricked out Saigas just yet but they do look promising.