I don't believe that the foundation-guys already sold their ETC's. It's possible that there is still some risk of a crash if they do it. But it's also possible that it would result in legal problems, because Ethereum started with a CFC and premine. To cash out on one chain, to make money and to damage the ETC-market - I don't know if that would be accepted.
that. is. glorious.
With the way things are progressing, ETC gaining users and value, ETH losing, ETC might become "the" chain, more secure and more widely adopted by developers. In this case the fundation would also have to go with ETC and I think they are well aware of this, so I doubt they would dump their ETC.