Once fully operational it replaces it as our best telescope. It can see further back into history than hubble can.
Hubble will be a spotter scope looking at areas of interest, then JW will look at those areas in detail.
Hubble might not be able spot what JWT can see. Everything we can detect or see, we have catalogs of as well as their locations or coordinates, but this changes all that. They're going to need bigger catalogs.
I hope the images reveal some spectacular objects...or maybe something beyond spectacular.