Bummer, but not a huge surprise. Ever After hasn't even been out for 2 years yet, I understand that they might want to take a bit of a break.
Not going to lie, Marianas Trench is one of the first things I thought of when I heard Save Rock and Roll on Monday. They've definitely gone in the same direction (though Marianas Trench have never had the same "punk" ties FOB had) plus Josh and Patrick are both amazing singers. But I don't think I'd ever want to see them together, at least not in Canada. When Fall Out Boy (finally!) come here I want them to be the headliners.
I'm not sure just how big MT are in Canada, but they would work so well as openers for FOB's US run. A FOB/MT/fun. tour would just be too much.