Once left ambiguously up in the air, the rest of the 2020 cruising season in the Great Lakes has been officially postponed until 2021, due largely to preventative measures taken by both American and Canadian ports restricting cruise ship docking to halt the spread of COVID-19.
When one of the largest players in the Great Lakes cruising industry, Victory Cruises, announced it would be cancelling its 2020 itinerary at the end of May, it became much more likely that others would follow suit.
Great Lakes Now
https://www.greatlakesnow.org/2020/06/covid-19-cruise-great-lakes-season-2021/