Those are valid points in the OP. I'd rather have a very varied bestiary than another big city and 10 levels of a gigadungeon. Monster models will be 3D and big cities will also need some 3D stuff, no? Will the big city 2 need some unique (creature) models as well? Is the team who develops creature art and models completely separated from the team who creates scenery art and models? There's 1,5 years left.
I think that's about my stance on this too. I too would rather have more beasts and fauna(be it plants and animals or demons and abominations) then simply more rooms to battle the same things I've already seen.
The peasantry... er, "nobility" here however claim that creature variety comes included with the extra content to be added via the stronghold, mega dungeon, and extra city. I state that such luxuries are lackluster "without" the above too. I personally have to take such things on word. But I think we can all agree on this.
A twenty floor dungeon loses some of its appeal if all you fight on all twenty floors of it are various "orcs".