After posting a similar thread on Reddit, I figured I might as well do so here. This is how I suspect the rest of the season will go based on how the current plot is progressing, and how Anet has handled previous stories.
The next story chapter is obviously going to take us to the northern part of Drizzlewood, where we will be continuing to follow Bangar, and trying to stop him from waking Jormag. We will obviously fail at this, and Jormag will almost certainly be awake by the end of the next story chapter. Bangar might die here, I could see him trying to use the bow to control Jormag, only to have Jormag just annihilate him now that his purpose is served, and all the Charr under him are Frostbrood. That, or he will be transformed into a Frostbrood champion by Jormag that we will either kill here, or later during the final battle. Probably the latter if anything.
The next two chapters after that will probably be the Icebrood Saga's "mcguffin" section. The Rata Novus/Thunderhead Peaks story segment where we go somewhere to find some specific magic/technology/knowledge needed to stop Jormag. They will also most likely have a shared map like Bjora and Drizzlewood. I am not 100% sure where this will be, Thunderhead Peaks was itself something of a curve ball with the rest of the season location wise, but given that I've yet to see any suggestion the world map will be expanded, and that the story so far has been up north, and that we saw a section in the trailer with centaurs and human slaves, we may see another map in the Woodland Cascades, covering the main center section of it.
The chapter after that will be the "fight Jormag" story section. Icebrood Saga's Dragon's Stand/Dragonfall map, where we deal with Jormag. Again, assuming they don't expand the map further north, this makes most sense to take place in that big ice lake area between Bjora, Drizzlewood, the EoTN, and Bitterfrost, as Jormag was already known to hang out around there back when Bitterfrost came out. I will also say this one will probably not be a two parter like Bjora, or Drizzlewood, but instead a single map like the other Dragon fight maps. I just don't see them splitting the big dragon fight meta into two separate, unconnected, metas.
Now, I will say that I doubt this will be Icebrood Saga's last chapter. Icebrood Saga is different from the previous LW seasons in that its called a Saga, a term used for a long, epic, story, and has a dedicated prologue chapter unlike LWS 2, 3, and 4. Long epic stories that have a prologue tend to have an epilogue, and I could easily see Icebrood Saga having an epilogue chapter as well, taking place after Jormag is dead, and leading into the upcoming Cantha expansion. The most obvious place would be the Dominion of Winds, with the Tengu deciding to open it now that four of the dragons are dead. This will end with them either proclaiming they are going back to retake their homelands in Cantha, or the Canthan's just attack for seemingly no reason, leaving us going "welp, time to go to Cantha to figure this out" for the expansion.
I will also guess that we will get Vision of the Past updates between Drizzlewood, and the next map, and between that map and the Jormag fight map, and these will show more of Ryland's action in between the story segments. Right off the bat I can see the next one dealing with Bangar's assault on the villages in southern Drizzlewood, and Ryland not being comfortable with killing all these people for no reason.
Ryland will probably defect from Bangar at the end of the next chapter, after seeing how badly hes screwed up with trying to reign in Jormag. That doesn't necessarily mean hes going to join us, especially not after what Smodur did, but I don't see him staying with Bangar.
With an average of 2 months between releases, and about 6-7 more releases before Icebrood Saga is likely over, this should take us into the middle of next year at the earliest, probably a little later in the year, and the expansion will come out a bit after that.