The trade volume of the ETC is quite low at the moment. I think the big dump has not started yet so far.
Or it will not happen. Charles Hoskinson has already committed in helping ETC get organized for the creation of a road map, build a structured governance, get developers to start working on the platform and finally provide funding for maintenance. Even if you are an ETC hater it would be stupid to dump now. It is better to wait for a better price to sell.
If the white hat hacker dump the ETC to the market and donate the proceeds to the ETH community, then it might not be good for ETC.
It will be bad only for the price of ETC. If the attacker and white hate hackers and the Ethereum foundation decide to dump, it will not kill the platform. It will live on. I also speculate that they will not dump. Why? Because ETC now has also a chance to become successful. They will now want to have a stake both in ETC and ETH.
I think only one of the Etheruem will prosper. Developers and business do not like to develop for two chains.
No. ETC and ETH will diverge and each will go on its own. So there will be no reason for developers and companies to build on both chains. I noticed that most Ethereum fork supporters want only one chain because their position is threatened by the original chain. Blame Vitalik for the fork. The original chain will live on whether they like it or not.
The Ethreum Classic price is quite high at the moment. If it rises further, it might attract some big dump. That is a big concern.