Yeah, I am expecting a future confrontation with the Thalmor. My only reason for thinking it might not happen is because having two different war questlines might be redundant.
Not unless it is done right.
I think the first two DLCs (Dawnguard including) will revolve around features that players have wanted for a while (enhanced vampires, werewolves, and dragonbone weapons have been wanted for a while and Dawnguard delivered), and once those are done it could add more global content like a great war with the Thalmor.
With this DLC I could see that maybe the Thalmor took the Imperial City, and you have to visit it and try to take it back; maybe with the possibiltiy of having the dark brotherhood's plot actually matter, and show the new emperor (or Titus Mede II if the player didn't do that)