I don't know all the logistics, but could Disney move the departure port for Alaska cruises to Seattle or even San Diego (probably have to add an extra sea day) since the Wonder is already there? It would definitely warrant no-penalty cancellations for current guests. Maybe that is just too much effort.
No, they run into two problems:
(1) US law requires a foreign-registered ship doing a round trip from a US port to visit a foreign port. There are no foreign ports they can reach except Canadian ones and those are closed to them. So unless they get an exemption to the law, not an option.
(2) It isn't just Canadian ports that are closed to cruise ships, but Canadian waters. All up the coast for some distance out are Canadian waters [see this map for reference: https://bcmca.ca/datafiles/individualfiles/bcmca_hu_maritimezones_atlas.pdf ]. A ship would have to go a ways around, the BC Inside Passage would be out of bounds, and even once they get up to Alaska geography would create challenges for them getting in to the region/ports without going through Canadian waters [see the where the line of Alask.BC is relative to where the Alaskan islands are and the Canadian waters are... geography creates a problem].
So, no Alaska cruises this year.