Since DMC 2 is what it is, there isn't a point debating about Argosax imo. He was painted as some kind of demon god, but it really just was to make Dante look cool. So he's probably dead for good and we will never hear of him again despite this important role in the demon world.
Unless DMC 2 is made non canon or a remake is made. But keeping as it is really stupid as it just make the serie even more confusing.