The people who are dumping the coins are the ones who don't want to switch to ERC20 token. That should be common sense by now. The don't have faith in the continuation of the project, so they just want to cash out at any price. Once the swap is over, the current price of the non ERC20 token, won't matter. It's a new coin and a new project. You shouldn't be worry about what the current coin is doing, it's all about what is yet to come. That's what you should be focusing on.