If Thomas Lennon isn't aware of what happened to Mxy, and genuinely isn't being cagey, then fans will have to rely on Supergirl's final episodes for the answer. The season has wrapped, and Lennon referred to the appearance as his "swan song", so that would presumably mean that's the last we'll see of him and that he truly doesn't know whether his character's survival was ensured one way or another. In the episode, Nia suggested it's possible Mxy was merely trapped from within the crystal, which could give hope to Supergirl fans that he made it through.
