The GDPR still applies and will continue to by default, as far as I know. After the transition period the UK would have the choice to repeal or change it but I'm not aware of any push to do so.
Given the transition period is to end in January 2021, very likely with "no deal" given the current chatter coming out of London and Brussels, the GDPR will only be in force for another few months. I very much doubt the "Vote Leave" gang will want to replace it with a UK equivalent with the same teeth.