For those interested:
Randi's wishes are that the JREF keep running in perpetuity, including after his departure in whatever capacity that might be. Steps have been taken to ensure that is the case.
There is no chosen successor, and there may not be. Randi cannot be replaced. Hopefully, what he does can be picked up by one or more people.
Lots of names have been bandied about here, but none of them have been asked to take over after Randi departs.
One I can assure you that will not take over for Randi is Penn. Neither Randi nor Penn would wish this, as Penn is not interested in heading an organization. Penn remains very close with Randi, but not in the capacity of successor.
Jeff, thank you very much for this clarification.
It spurs my following thoughs (weigh them as you choose)
JREF needs someone to step in as an organizer when Randi dies. The Skeptic Movement (there, I've said it) needs someone to herd all the cats in the same general direction.
JREF forums could go to Shermer's site. The Challenge could be trumpeted by magicians everywhere, both high and low profile. TAM could become more widespread, coordinated with Dawkins, Hitchens (yes, I know), the Mythbusters, Criss Angel's site, and the participants of the Skeptic Web Ring.
Efforts would be focussed more, such that RS Lancaster and CFLarsen weren't kind of hanging their own butts out there, and grass roots education of kids, and media exposure could become more coordinated.
(Here's a barrell of good ole Canadian Crude for the fire) I am reminded of Girl6 and her passion for Skepticism.(Kiless, Athon, Teek, Rebecca, Wolfman, etc. please don't take offense) She contributed immensely to the JREF. Involvement with the first Skepchick calendar, the first TAM, bringing skepticism to disadvantaged inner city children in her area....
I don't mean to say she should be "the one" as I'm sure she has a life and stuff. What I mean to say is that I, personally, would like to see an organizer who has passion for this such that the herd of cats sees why they need to stay in line (and is not afraid to contact any cats that they think will help the quality and dissemination of the herd), and has passion for this such that they are constantly putting themselves in the front line as well.
My 2 cents (Cdn) for whatever that may be worth in your currency.