Hm, the OP of this thread makes no sense to me.
What does the modding capability of the engine have to do with DLC? DLC is made by the developers of the game who have all the game building tools at their disposal. Of course they can make new content.
(Besides, there are already people who make progress on taking the engine apart.)
Even if you are right and the engine was chosen to discourage modding, why would they do that if they weren't going to release DLC? If there was no DLC, why be opposed to mods? It's the other way round, that game company suits often see mods as competition for DLC (which is still flawed reasoning by the way). So that argument is completely the wrong way around.
Also, when was DA ever meant to be mainly MP? If anything, the MP seems slapped onto the game to me, which was mainly designed for SP.
Sorry OP, but I think you are wrong on all counts and I would be really surprised if we wouldn't see some DLC for this game. One can only hope that they'll do some patching first.
On a side note, I think it is admirable that BW finally got their act together on DLC policy (no day 1 DLC, no locked content in the game so far, etc.). Someone tell Ubisoft to take note.