Trey could come home, Princess could abandon Ivy and Trey & Princess could work on babies of their own (well, maybe their own
), Ivy could go back out to Jules (if she hasn't found a man yet)
Princess could nest, have eggs, Trey could come home, she could abandon eggs and start all over again with Trey, Ivy goes home (same scenario as above) ...
Princess could nest, have eggs, Trey could return, Ivy could be unwilling to give up "his" new territory, testerone tantrums ensue, someone wins, someone loses but hopefully not loses fatally ...
Princess could nest, have eggs, hatch out chicks, raise chicks, fledge chicks, migrate south, migrate north again, hook up with Trey and Ivy has to explain his absence to Jules (if she'll have him) ...
Princess could nest, have eggs, hatch out chicks, raise chicks, fledge chicks, migrate south, migrate north again, hook up with Ivy again, raise chicks again ... and their chicks turn out to be just as successful as Princess' and Ivy's kids
Princess could nest, have eggs, hatch out chicks, raise chicks, fledge chicks, migrate south and not be heard of again. Ivy and Jules return, Ivy knows what he is doing now and they have the best territory in Winnipeg and a new reigning pair are in power ... and its a smooth transition from one pair to another rather than a site in contention and no nesting pairs!!
... there are probably more scenarios, but those are the most probable ...