DTW doesn't make sense for WJ because if they wanted to attract passengers from the Canadian side of the border, those passengers would have to drive across the US border, clear customs, fly from DTW and clear Canada Customs at whichever airport they fly to. They are better off flying into Windsor, or at least starting with Windsor before DTW in order to serve domestic passengers. Windsor has some potential to attract Detroit passengers, DTW won't attract Windsor passengers.
I bet it will be at least 2 or 3 years before WJ goes into the USA, probably longer. They have already said the western Canada market has potential for them to have up to 30 aircraft, and the east represents even more potential than that. They have some major growth from 14 aircraft before they will reach the point they want to fly into the USA.