I imagine at the end of the dungeon a construct springs to life with a mention of how many millennia it has been since "our" last visit. Cue the puzzled look on our face when it spouts broken bits of lore and then we have a vision of events from the past.
The echo vision of the Exarch reading the Heavensward tome also still needs to be addressed. Insofar as I remember, we have never had a vision of the future using the Echo. We even question what that was when it happens to us.