Not to stretch too far off the topic, but I think it will be enough for the Canadian government to get around to replacing its heavy icebreaker fleet, without getting into opening the Seaway year round.
As for container ships going into the lakes I do not see it happening. The ports of Halifax and Montreal do a very good job of transferring containers to trains and moving the boxes on to Toronto, Detroit and Chicago. Yes many also go by truck, but that is inevitable.
The Seaway is a much slower way of moving cargo, and I don't see the economics of transferring containers from ocean going ships to Seaway ships instead of trains. Also the cost of making the Seaway a winter operation would be enormous.
But back to icebreaking. What is really needed is a top class icebreaking fleet.
I read today that the new CCGS John G. Diefenbaker will not work south of 60.
Meaning it will not do winter work in the Gulf or river. All the more need to get some new ships going soon!