Thanks to "That Shaman" we now know there are 9 slots in the Icebrood Saga portal tome. One for the prologue, and the other 8 for the rest of the season episodes.
Re-watching the Icebood Sage trailer, we see
1. Charr lands
2. The Shiverpeaks
3. Centaurs in what is likely the Woodland Cascades
4. Some watery area with a sinking ship
Presuming Anet is going to stick with this "release a map in one patch, then expand on it in the next one, then move on to a new map" thing we saw with Bjora Marches, we are going to get two episodes in the Woodland Cascades, most likely in the arena bordering the Shiverpeaks, and another two in the Far Shiverpeaks, somewhere between Bjora Marches and Bitterfrost Frontier, when we go fight Jormag.
That still leave one set of episode unaccounted for however. Maybe we will get another map in the Charr lands to deal with some sort of minor civil war caused by Bangar's action?