I've heard 40-60 hours.
RedEyesBlackGamer said:
They said it was going to be shorter (and shallower. No! Bad Red Eyes! Stay positive!). Hack n' slash combat is conducive to shorter playtimes. I'm guessing 12-15 hours for an average playthrough.
Have you seen gameplay demos? The combat looks pretty much the same.
The major changes have to do with the semi-predefined character (dialogue included here), the leveling (I've seen the new skill tree, but not in great detail. I know it is different, but don't assume that means shallow), and the story (set over many years, not the typical BioWare epic).
There are also race redesigns. Elves, Dwarves, and Qunari looked like humans in Origins (pointy-eared humans, short fat humans, tall and brawny humans). They're making them look more unique and fantastical. It is fantasy, after all.