I'm not exactly sure what makes a game 'indie' exactly, but as far as I know No Man's Sky is being published by the developers, Hello Games. I think Hello Games has about ten employees. Take it with a grain of salt because I don't entirely know what I'm talking about, but if ten people are developing and publishing the game I'd say that probably counts as Indie.
If that is the case, I guess it could change between now and June though. I imagine developing a game and publishing a game are two very different challenges. That's not to say the folks at Hello Games aren't capable of doing both, only that it wouldn't surprise me if they outsource the publishing side of things to a more experienced company.