The Disney Wonder can hold a lot more than 500 people, so it's included in this deferral. But Alaska isn't part of Canada, and the US hasn't prevented cruise ships from docking in it, so why does this matter? Well, the Wonder's cruises to Alaska are homeported in Vancouver, which is conveniently in Canada. As a result of Canada's restriction, the first Alaskan cruise of 2020 on the DCL website is at the start of July. Disney's Alaskan cruise season typically starts in May or June, so this is much later than usual.
Interestingly, all of the Wonder's May and June cruises aren't listed on the website. The previously-scheduled itineraries in May and June haven't been altered, they've just been cancelled. The Wonder will be doing nothing from the end of April to the beginning of July! If the current cancellations aren't extended, the Wonder will do a few cruises in April, then likely stay docked in San Diego until July.
It's possible that the May and June Wonder cruises will be changed into Mexican cruises from San Diego, like what the Wonder does before going to Alaska, but I think this is unlikely. These potential cruises probably wouldn't sell well because of the coronavirus. To get more people to go on these possible cruises, Disney will probably lower the prices, but not by much. The company's called Disney, not Discount.
I'll keep my blog updated as I find out about any changes to the DCL schedule.