I wouldn't count on the Canadian border being open again until the rate of infection in the US drops to near the level in Canada. We just may get that border wall that some folks have wanted, but it will be with Canada and they'll cheerfully pay for it...
But, to be more serious, the reality is that travel to Canada or Australia is simply out of the question unless and until the US can show that US visitors aren't a threat. Sad, but that's the way it is. If you are thinking about a cruise to Alaska, it would be better to book one from Seattle, and be sure you buy cancel-for-any-reason insurance. Or, just wait on the idea entirely, since it's unclear whether there will be a cruising season this year at all, from Vancouver or from Seattle.
Booking a cruise out of Seattle for Alaska - would be flawed - Cruises originating in the USA and returning to the same city (Seattle) require a
port call at an international port (namely something in Canada - usually Victoria BC) before that re-entry to the USA.
This a requirement of the PVSA - not to be confused with the Jones Act {cargo}.
With this noted that port call in Canada would be the same as any other cruise involving travel to Canada.
Cruises probably won't take place until summer at this earliest - who knows what that Magic Crystal 8 Ball and Ouija board will predict !
This covid virus 19 has to be well under control before any cross border - cruises - train trips - flights - are going to be viable acceptable to Canada.
Caution about booking any cruises - watch the requirements for payment refunds credits --- tricky stuff with cancellations and rebooking !
The Rocky Mountaineer would be one activity suspect in operation -
Not many folks take the Winnipeg Churchill trip -
The Canadian train trip from Winnipeg to Vancouver -
Anything from Montreal to the maritime provinces
Alternatives -
Fly to Alaska and take the Alaska RR from Fairbanks to Anchorage - extension to Whittier or Seward -
do a self guided tour to get training out of your system.
The Mexican Rivera maybe opened for cruises before Canada (But no Train activity)