Many of the gamejam add-ons have made it into the game. Any word on water current, movable platforms, pitch black, etc. dungeons in Dawnguard?

I expect things like moving platforms to be in the DLC dungeons, since they can't be added to already existing dungeons, and they aren't a new feature (just a new element)

Pitch dark dungeons however requires a bit more work, but considering that the DLC seem to have a darker theme, I suppose dark dungeons would be a nice new element for Bethesda to add.

Maby if they add pitch dark dungeons i would use the lighting spells, i lowered my brightness all the way down and still it's too bright.

I love the fact they added some gamejam elements into dawnguard such as the vampire lord, yet some were not shown in the trailer. I really hope they would add the house building.

Not really. When you create a cell (like, say, a dungeon) you set the base lighting levels for it as one of the first things. It would be very easy to just drop the settings to make the room pitch black. They didn't do it for gameplay reasons, rather than because it was hard.