From what I know, the current legal consensus is that this is not possible (despite not being explicitly mentioned, which really seems like a strange oversight, but it's seen as being obviously the intent of article 79) – the only way to get rid of it would be to replace the Grundgesetz with a new constitution. (Some argue that since the institutions that could replace it are bound by the Grundgesetz, them enacting a constitution that doesn't provide the protections of article 1-20 would not be legal, but that's further in the realm of untested theories)

And of course, changes like this would be likely to happen in political environments that don't care about these things.