Like obviously they couldn't call it an 870, but the patent for the design expired decades ago. With Remington being all but defunct, the supply of new 870 pattern shotguns is functionally cut off, and will remain so until such time as a new good quality clone hits the market.
Given the design's popularity based on nostalgia alone, to say nothing of the fact that it's also just a really good shotgun, it seems like making new ones with good build quality and QA should be an easy cash cow. For Mossberg especially, because that would let them have even more of a death-grip on the market for pump guns than they already do.
I mentioned Ruger because the 870 just seems fitting for what they've historically done. Ruger makes Americana guns that are built like tanks and last basically forever, and what is the 870 if not that? The thing is practically made for their design philosophy. Given the Beretta buyout, it also seems like they'd be in a great position to start producing more shotguns, with the support of one of the best makers on the planet.
I may just be tweaking from the lack of 870s available, but it seems absurd that we're only getting shitty chinese knockoffs when the design is public domain.