As far as I'm skeptical about fans reveals on the plot or assumptions of the projected game/additions, it's worth to mention that before Inquisition was announced (or at least at it's early development stages, I'm not quite sure now), most of the companion names and origins were known because of the Internet leak. Therefore what we see in opening post could be some kind of "trial baloon" to check the community feedback on some aspects of the expansion.
Apart of that aspect, if not fake, the plot outline to expansions seems quite reliable, as it mach to post-credit scenes and will possibly crown the themes between Inquisitor and Solas (that he helped you to gain the control of the mark that could kill you because of his acts, and then hunting for the Orb he wanted to recover...). When reading the "expansion plot" it seems quite possible that Solas had found something similar to Orb or another elven artifact to recover the power of gods and his kind and possibly his acts will make an impress on the Inquisitor mark - or he simply would like to lure Inquisitor to him as some kind of a "vessel" or "seal" that somehow gained the power of elves at the conclave.
What's more about the Fade it would also match if we discuss about person that stayed there after the siege of Adamanth. I wonder if we will be possible to do something about it (you know, that statement that "X would most likely...") with help of Dreamers?
Thats of course just a speculation, but for sure the plot of Solas and his actions after the final battle simpy have to find it's final somehow in game series, so it would be an expansion to DA: I at some time.