apostrate,
It's interesting to note that although some Bible Students organizations are still around the Witnesses are the only ones who grew to much larger numbers. That too was Rutherford's doing. "Advertise, advertise, advertise the King and his Kingdom!".
I bring that up because the larger a group becomes the less likely they are to completely disappear. I think however that the Witnesses are so tied in to their governing body that no one is likely to become a new leader of a JW sect. Either way it would be interesting to see if they implode and how.