I'm currently running Curse of Strahd and plan on extending the adventure beyond the end of the published material. There are a couple of areas that the party have not gone to and I do not expect they will go to before finishing the adventure (so I can include them in my extended adventure so we get to see everything), but otherwise, I don't want us to be just going through the same old locations again; I wanted to add some new areas and extra content.
Looking at the map of Barovia on p. 35, I can see that the left and right edges of the map are likely the edges of Barovia, since the right hand edge is labelled A, which is where the party first arrive after walking through the fog (which I take to mean that going back in that direction just leads them getting lost and spat back out into the map, as per "Mists of Ravenloft", pp. 23-24), and the left hand edge is likely more of this fog, given the description in Chapter 14: Yester Hill (p. 200):
Any creature that enters the deadly fog is subject to its effects (see the "Mists of Ravenloft" section in chapter 2).
This is the reasoning I'm using to conclude that the left and right edges of the map really are the edges of Barovia itself, and that there is nothing further in either direction (although, if I'm wrong about this conclusion, I'll happily be challenged on that in an answer).
My question, however, is about the top and bottom edges of the map. At the top of the map is Mount Baratok and the various locations marked M. The bottom of the map is Mount Ghakis and a road that leads south from Amber Temple (although this could just lead off the edge of Barovia like A and road that leads west from Krezk, but it could be a road to somewhere else in Barovia). There's nothing written in this adventure that implies that these are the edges of Barovia itself (yes, there's the "fog effect" around the edges of the map, but I assume that's just for style, since otherwise Barovia is a neat rectangle shape - unlikely).
Of course, I as the DM could just decide that these aren't the edges of Barovia as that suits my purposes, and if it turns out that these are actually edges of Barovia, that's likely what I'll do, but I wanted to know if there was anything published about Barovia (likely from older editions of D&D, but if there is anything I've missed in 5e, I'd prefer that) that describes what might be beyond the edges of the map. Are there any maps in previous editions that roughly match up with the map in Curse of Strahd, but that shows anything further north and south, or anything I've missed in Curse of Strahd?
Another way of asking this might be "is Barovia the same size as the map, or is Barovia bigger than the map"? Also note that I'm interested in Barovia as the demiplane1, the Domain of Dread, not anything relating to what is was back when it was presumably a place on the Material Plane before Strahd and the Dark Powers happened.
1 I'm interested only in the area referenced as being "spirited away" (which is hopefully bigger than the map on p. 35) on p. 9:
[Strahd] had destroyed the family bloodline and doomed all of Barovia. The castle and the valley were spirited away, locked in a demiplane surrounded on all sides by deadly fog.