A new expansion is scheduled, we know it. What we don't know is what will be inside it. The 2.1.0 Patch may have provided a beginning of answer to this question !
In the patch .MPQ file, there are a few terrain models, that you might have already seen. As you can see they're in the Expansion02 directory, which is quite unusual for not yet released content (most of it is in the same directory as the normal content). Obviously, the Expansion01 directory only contains Burning Crusade files.
"Howling Fjord" is a region located in south-eastern Northrend. Men who were left behind by Arthas have setup the Valgarde outpost here.
There is also something else, Northrend loots. Two files of the patch are already labeled as loots from Northrend (shield_northrend_d_01.m2 and sword_1h_northrend_c_01.m2). There are multiple skins for each one of them.
This leave us with one question : Why Northrend instead of the Emerald Dream ? Some of the map files of the Emerald Dream have been in the .mpq files for ever !
There is a simple awnser to this : Why not both ? You can enter the Emerald Dream from 5 portals, 4 of them are already known (Ashenvale / Felwood / Hinterlands / Feralas) but the last one is in ... Northrend ! Crystalsong Forest exactly.
This could lead to the release of an expansion scheduled as Burning Crusade, a new continent with an inaccessible final boss (Illidan in Burning Crusade, Arthas in the case of Northrend), but with something to keep you busy while the new dungeon is added (Emerald Dream).