I'm not so certain. GX was unique in a lot of ways, but it was common goals and interests that truly transformed the Xavax from a disparate group of refugees into a unified people. Be attacked from all sides engendered a deeply rooted sense of personal and national pride among them. All I really did as a player was take advantage of what was already there, like a conduit, so I think that any character could have filled Selenia's role. Even though she's withdrawn, I still get the feeling that what made them into a unified people is still there, even though they've devolved into idealistic factions, New bloods and old, pro-sirion and anti, Selenist and separatists, they all want the same things in the end. So long as they keep wanting those things, Xavax will endure in their hearts and minds even without the physical realm. They never really splintered, you see. Their faith keeps them together.
That said, I still don't think that some version of "New Xavax" is a good idea, at least not politically. Besides, they're missing a pristine opportunity to make "Xaligus" a thing.