Inquisition was not a raging financial success. For all the hype and the GOTYs thrown at it, the reception from the general gaming community has been lukewarm. And I think sales reflect that.
It's been three and a half months since release and the only DLC news there has been is a vague "we're working on something" comment. Whereas Origins and Dragon Age II had story DLC released or officially announced already by this point.
Then there's the news of Gaider being shifted to another project. Now that could have a million different meanings (as could their cancelled project) but for a studio with supposedly wind at their back and more Doritos-approved accolades you can shake a Mtn Dew bottle at, they have been uncharacteristically silent with their marketing and advertising.
Perhaps it's a directive after the disastrous Dragon Age 2 and Mass Effect 3 marketing campaigns. But I sense all is not well in BioWare land. Mass Effect 4 might make or break them.
Of course I could be wrong, just an opinion.
I thought they claimed it met their sales goals or some such? I know a lot of people are divided on it, I personally felt it was better than 2, but worse than Origins because none of the choices mattered (you never got to see any of them have any sort of lasting effect) and you couldn't do anything evil, which really ruined my Palpatine inspired character 
After a couple months of thought, I'd classify it as an Action-Adventure game with a character creator before I would an RPG, just my opinion though. I still enjoyed the game, I enjoyed it a lot, but it didn't feel like Dragon Age to me.
As for the DLC, no idea. I'm guessing that they might (still) be struggling with the Frostbite engine.
I'm not too concerned about Gaider's departure though, if he had left the company I would have been, but the fact that he is just switching to a new IP... That makes sense to me, considering he's been working on Dragon Age for nearly 10 years, that's a long time to work on a single universe/project.
They have been extremely silent though, I concede that.
I do fully agree with you in regards to the next Mass Effect could make or break them. I figure that they'd be done for if it bombed.