Factorio has been around in "open beta" for something like 4 years now (and I've been playing it for at least 3), so I suspect it'll be around a while longer.
However, even if the developers stopped updating the game, so long as the game runs on your PC, does it matter? We have people doing crazy things like effectively emulating DOS in Javascript so that you can run DOS programs in a browser window (see archive.org's DOS game section); somehow I don't think you need to worry about not being able to play it in a few years. It's all local by default, so you're not having to worry about someone taking the game servers offline either.