Seriously, are they closing with ACOT?
ACOT? A Change Of Tuscany?
Seriously though, I can see the encore being "A Change Of Seasons" only because if they stick to the one-song-per-album scheme they've built the setlist on, then playing "Octavarium" would mean having done TWO songs from that album, but doing ACOS means they've covered 11 studio albums and their studio EP.
Also, IIRC, the last time ACOS was played in full was on the Train Of Thought tour, where as 8VM was played more recently, so I think it's time to bring back ACOS.
-Marc.