Their control over elders and publishers is too strong to allow a splintering to occur. For any significant splinter group to form would require a freedom for members to express what they feel and gain the sense that there are others who share their view.
The threat of disfellowshipping for any who step out of line and challenge the authority and teaching of the GB is far too strong to allow any more than a handful to leave with the intention of starting something new. I just don't see it as feasible that people would be prepared to accept disfellowshipping, with all the shame and humiliation that entails, to join others, particularly when the level of rhetoric from the WTS against the "rebels" would skyrocket.
Could it implode? I just can't see it. The movement has a momentum all its own, fuelled by the myth of divine authority and the fear of expulsion and eternal damnation. It also has its own centre of gravity that keeps pulling members (and recruiits) towards it. Few of those ever stop to examine the logic and teachings of the organisation, and because they're not allowed to read or hear criticism, they have no yardstick by which to judge it.
The internet and media exposure will cause some to drift towards the edge and leave, but the machine will keep rolling on.