I'm assuming you mean what if a clan founder simply stops playing and stops using Bnet. Well depending on the freedom they've given the admins they can pretty much run it themselves. However they can't be reseated as a new Founder can only be appointed by the current Founder. If the Admins have very little administrative power, you can always choose to remake the clan and move its members. But you're likely to lose people this way, if most even agree to it.