Rigel is still a Main Sequence star, fusing hydrogen in its core. It needs to progress a bit in stellar evolutionary terms before becoming a supernova candidate.

Nearby Orion supergiant Betelgeuse is a much better SN candidate. It has evolved past the Main Sequence stage and is fusing heavier elements. If massive enough, it will pass through the stages of fusing helium through neon and all the way to iron, at which point nothing more can be fused and core collapse will produce a SN explosion.

The important thing about Rigel is its youth. Vance woke up to this fact after writing Star King and created the mystery of the Rigel Concourse to get around the fact that Rigel could not have a family of such old, mature planets. He did correctly mention Rigel's distant stellar companion, but he seems to have been unaware that Rigel B is a binary and would have appeared as a brilliant stellar pair orbiting each other in a period of many years.

Betelgeuse is about halfway between Sol and Rigel. If and when it goes off, it will be similarly bright in the skies of Earth and the Rigel Concourse planets -- about as bright as a crescent moon, bright enough to cast shadows on a dark night.