Make sense that they will start liquidating ETH towards their mainnet launch.
They will need to fund things, marketing, scaling things up, and etc.
Well, all we are just basically doing here is to speculate without any single proof of EOS team dumping ETH for real and even if they have decided to dump ETH for EOS, it is their market and they can decide to do whatever they like to get the coin supported, and I believe ETH is strong enough to keep itself going. However, I do not see how all these actually sum up with what is going on in the market presently, and I may be wrong, but it does not seem like real news.
What makes OP thinks that the EOS team is dumping ETH. At least even if he is trying to share something he must have read somewhere which to me is more of fake news, probably next time, he should share the source. The whole market is in correction, it is not the first time, and it would not be the last, so looking for reasons for that is absurd.