I don't think anyone will be able to top rms in charisma, in the sense of having that feeling that Free Software is their calling in life, above anything and everything else.

That said, I think a movement only needs a charismatic founder to keep going for centuries with more regular leaders. I think there are a few worthy candidates, like Eben Moglen, Karen Sandler and Mishi Choudhary, and I'm sure a few more can be found in the FSF ranks themselves, now that obfuscating spotlight is gone.