When the new ships are added, one may serve the west coat in a more dedicated fashion. I don't know if anyone knows. The thing about Hawaii cruises is that they either need to leave from, or stop at, a non-US port, and that's a bit of a nuisance to build the itinerary unless they run them out of Vancouver, and that's not something they'd want to do year-round.
There are weird US rules about ship staffing and registry if a ship starts in the US and only stops at US ports.