Just like the first poster already said, you misunderstood the whole thing, eth 2.0 isn't a new eth coin, there will never be two different eth coins in the market except some scammers or some hungry developers make a clone, the much awaited eth 2.0 is just a major upgrade that will be applied to the current Ethereum network to help scale it further so as to help bring down the high cost of transaction fees which have been a major problem if the blockchain is last year, it will also be moving Ethereum from being a pow coin to POS, this means that Ethereum can no longer be mined but staked.
So for me, I think the release of eth 2.0 should rather cause eth to highly increase in value rather than come crashing, the release of eth 2.0 will be the best news for Ethereum supporters and users.