In the game data, they hint at a map called "Bird God.
The map has not been officially announced. The only knowledge that we know of in regards to this map is that it might exist in the future. If you look in the Sunset quests, you will see that there is an addition: "Bird God."The obvious predictions are that it is going to be including the Bird Cannon at Sunset (this map=Sunset as Rainbow=Snowman as Twilight=Pumpkin as Deep Sea=Coral).
One prediction that also comes to mind is that this is the surprise TL has planned for the 2nd Anniversary Update. What else do you think is going to come to place?
Also, do you think "Bird God" is a working title for the map?
EDIT: I also think, for the other map slot, the map would be a Ketchup Avenue retcon.