Exactly, the after credits scene means it's no longer just a side thing that doesn't matter.
I'm actually curious now as to weather or not the old god soul is going to be the ultimate factor in the future here. It sounds like at the end Solas went to absorb Flemeth because the people, presumeably elves needed him, however we don't really know if he knew about Flemeth(Mythal) using Morrigan and the Hero of Fereldan/Alistair for the dark ritual.
Now since Flemeth is Mythal, she knows what Solas (Fen'Harel) did to the ancient elvan gods, assumeing the other stories are to be believed, she would likely also know the dread wolf would find her eventually, putting an end to her, and she wouldn't be able to stop him. The dark ritual could have been Mythal's plan to trick the trickster all along, and when he went to absorb/kill her, it allowed her to take over him instead.
Maybe I'm going too much into this though, but I feel like they wanted the dark ritual to be a major factor for the series, and this could change everything. Instead of Solas trying once agian to set things right, we would have Mythal freeing the other elvan gods upon the world. But if that was the case you would need two almost completely different stories for the next chapter of the series.