I don't see how you came to this conclusion.
Actually, he could be right.
Look at the in-game skyrim map. Notice that on the other side of the mountain range running from Falkreath to Markarth, there is a very large area continually covered by clouds - but it's also an area that is highly suggestive of large open spaces, possibly plateaus or high valleys with mountain ranges on the west and east. This is highly suggestive of a 'corridor' running between the hammerfell cities of dragonstar and elinhir in a sort of NE-SW axis.
From the last thread, the speculation tended to favor Dragonstar as a possible location for the next DLC. Per the in-game map (which differs from the old Tamriel map from Oblivion days), Dragonstar would likely be directly south (or, at most, SSW) of Markarth, across the first range of mountains. Elinhir would be just south and west of the gate at the very southern end of Falkreath's province. In between these two Hammerfell cities would be almost certainly the location of Orsinium, which per current lore is right on the skyrim-hammerfell border and no longer located in proximity to or within High Rock.