I was under the assumption a Jedi (or a Mandalarian) would eventually kills him. In The Acolyte they have this exchange: ​Osha: “You speak as if you were a Jedi.” ​Qimir: “I was. A long time ago.” ​Osha: “I’ve never heard of you.” ​Qimir: “It was a really long time ago.” So Jacinto’s cortosis-using dark sider could be an early minor apprentice of Plagueis, one of their experiments, or a Sith acolyte Plagueis is scouting. That way he could be long-lived enough to appear in the New Republic Era since The Acolyte was canceled. So since we know Palpatine’s consciousness is alive in a strand-cast on Exegol (since Mando & Grogu precede episode 9), for my money Qimir could make for a good new Vader.