I haven't been on the server since January at least. I've thought about it, but much like playing the game in general, I don't know what I'd even do while there. I'm not much of a builder, and there's not much else to do besides mine and build things right now.
I'd say the game isn't even half finished yet. Any estimation anyone could give at this point would just be a wild guess. There's a good amount of art assets and potential, but the actual game part of it isn't close to done, unless you just want to build things in 2D.
I wonder if they regret releasing last year. Seems to have been a ton of loss in momentum and enthusiasm over the last several months. Just glancing at Steam stats, I wasn't expecting Terraria to have so many more peak players than Starbound. But then Terraria has interesting gameplay, whereas Starbound currently just has potential and better building mechanics. I'm still looking forward to what's coming, but it's been slow going.