The more I think about it, given her pregnancy and DC's attitude, if AM had remained with the show, it really would have been likely that she would have sat out the 1897 storyline on maternity leave and then returned for Leviathans. Though that still leaves open the questions of what would have happened when it came to 1970PT, 1840/41, and 1841PT? But then, had AM remained with the show, who even knows if those storylines would have taken place because they may have written the show very differently with AM still a part of it. Leviathans may not have even taken place.