GDPR is incompatible with bitcoin blockchain as it is an open blockchain network. It is not possible to delete or modify previous data of a blockchain.
Available options are either EU has to change their GDPR rules and exempt blockchains including bitcoin from the new rules or blockchain developers have to develop blockchains which are compatible with GDPR.
I don't think bitcoin blockchain's technology will change to comply with GDPR.
EU has to exempt bitcoin from GDPR.
However, centralized cryptocurrency exchanges, merchants that accept bitcoin payments have to comply with GDPR when dealing with customers' personal data.