The key word in central bank digital currency / CBDC / digital dollar is - central.
While now people have some anonymity when holding cash and with some credit card transactions the CBDC currency removes anonymity and knows about every single transaction.
Moving from CBDC to crypto and back depends on the CBDC issuer allowing this.
Judging by the actions of China - outlawing mining and trading in crypto it will not be possible. Other CBDC issuers will take most likely the same actions.
When CBDC-s become dominant in the world the existence of crypto-currency will depend on existence of a parallel economy where producers of goods are willing to accept payment in crypto.