A new rumor from EN Stars suggests that the seeds for destruction in Thor: Ragnarok may be planted in next summer's Avengers: Age of Ultron.
"It's also highly unlikely that we'll see Thor involved in the events of a Midgardian Civil War, likely because he'll have his hands full dealing with his own kingdom. We know from the clip above that Thor leaves the Avengers to work on his own after their encounter with the Scarlet Witch. It's possible that whatever dark vision Wanda puts into Thor's mind sets him on the path back to Asgard. My initial response is that Thor's vision may reveal Loki's treachery to him and while I think he'll obviously return and help the Avengers defeat Ultron, I won't be surprised to see Avengers: Age of Ultron end with Thor sitting on the throne in Asgard, having banished Loki. We know we'll see Asgard, or at least Asgardians in Avengers: Age of Ultron, as Tom Hiddleston and Idris Elba have recently been revealed as cast members, so it's certainly not unreasonable to speculate about Thor being off-planet for a while during that film and why he will likely be absent during the events of Captain America: Civil War."
EN Stars suggests that Elba and Hiddleston's scenes will focus on a scenario very similar to the one I envisioned, "The rumor around this scene is that Scarlet Witch could use her telepathic powers to show Thor what Loki did and what Asgard has in store for him. This could lead to the hero leaving Earth and going to Asgard to save his people."
If this rumor turns out to be true and the God of Mischief is indeed responsible for the fall of Asgard as I speculated above, that means I didn't miss by much. I know I miss a lot, but I also take a lot of swings. If I hit on this one, just do me a favor and remember where you read it first before it became a rumor and before it became part of the MCU!