Currently it's known that there will be at least one more release which is Among the Stars: Years of Peace.
This is useful, thanks.
Even if there is nothing else planned there is a ridiculous number of cards and optional ways to play to keep the game fresh for a very long time.
This is correct.
Just because there are no longer any expansions being produced for a game does not mean it is not a good game to play.
Moreover, some great games don't really get much in the way of expansion support, ever...(c.f. Goa, Key Market, Vikings and so on.)