EU citizens will almost certainly not need a visa to visit the UK, no matter what the final circumstances of Brexit.
However, like other countries that do not need a visa to visit the UK, border agents could still refuse entry if they believe (for example) you intend to seek work rather than just visit.
I am glad that you, as an EU citizen in the UK, are not panicked.
However, in many cases the panic already exists, in no small part because the people running the UK refuse to be held to their own previous promises, even when it comes to what they want from Brexit.
However, like other countries that do not need a visa to visit the UK, border agents could still refuse entry if they believe (for example) you intend to seek work rather than just visit.