During the Credits
There are no extras during the credits of Dragon Age: Inquisition.
After the Credits
No matter what choices a player makes, the same extra scene is shown after the credits of Dragon Age: Inquisition.
This ending is a bit confusing and actually could mean one of two things. Either Flemeth is a vessel for Mythal, who came to her from the Fade/Beyond and has now taken over Solas’ body or there’s a chance that it’s the other way around. What is actually happening will likely be explained in future DLC or the next game.