"Linux gaming" is already a very small subset of "PC gaming". This atari box will necessarily be a smaller subset of linux gaming. I don't foresee any developers going out of their way to compile/package games specifically for this system unless they were already planning a linux version for GOG/steam distribution.
So at the end of the day, there's probably not going to be anything you can do on this atari console that you couldn't do on a similarly-specced linux PC. Meanwhile, there are certainly going to be *lots* of things you can do on a linux PC that you won't be able to do on the atari.
While the price is fair for the hardware, it's still well outside the realm of "impulse purchase" for a console with such an inherently limited ecosystem. I really can't see this thing selling well. I honestly wouldn't give it more than a 50/50 chance of even making it to market, and perhaps a 1 in 10 chance of the company still being in business a year later.