HI: I'm not an expert but it is my under standing that the old tokens will be converted to new ones based on what EOS sees in you wallet which will be visible by using your MEW public key. Your MEW wallet must be registered so EOS knows who has the old tokens. When the EOS blockchain is launched you will access your new tokens with your EOS public address and EOS private key on their newly created block chain. If I'm wrong someone please correct me. Thanks.