The big winners will be the people that were standing on the side lines and wanting to get into the airline business. There are always people with money that want to spend it on owning their own airline.
I know of at least two new airlines in Canada that are poised to start up with non domestic services. This development makes room for them to get into the domestic market now also.
As for JetsGo passengers and whether they will thank WS or AC for rescuing them. I just saw a bunch of very sad people in YYZ T1 that heaved a big sigh of relief when they got boarding cards on AC flights home.
I think that AC handled the PR angle properly this time. They were already very full and do not have a lot of inventory to sell. The worst thing to happen (as has happened before) is that the JetsGo ticket holder gets too high an expectation that some other airline will come along as a saviour and take their tickets for free or allow them to buy a ticket comparable with what they got from JetsGo. This time they did not clog up the airport ticket counters clamouring for AC to 'Help them out' as the expectation has been built. Watch the bad feelings if the passenger is expecting a good deal and then get to the airport and find out there are no seats available except full fare Business class.