Good question, it looks like many layer 2 projects will be abandoned after Ethereum merge and PoS is active but I don't see things that way, I believe whatever will happen depends on project builders ( developers ), we can't tell them to start building on Erc 20 if they believe that Matic is the right place to be, see? Layer 1 and 2 projects will survive because many developers will still prefer them than Ethereum.