The phenomenon of electric current superconductivity is well known and there are even talks about color charge superconductivity.
Is there a context in which gravity superconductivity makes sense? It seems that all known bosons have gravitational attraction (even if they are massless) so we should expect all matter to be gravity superconducting. At the same time, all materials seem to be transparent to gravitational interaction so maybe it is superfluous, since normal conductivity happens in condensed (non-transparent) matter. The actual effect is expected to be very small before stellar scale.