"Thor: Ragnarok" may arguably be the turning point for Phase 3 of the Marvel Cinematic Universe.
As Captain America has run its course, the focus shifts to the god of thunder as the battle moves from Earth to the cosmos. Doctor Strange may be the link to both worlds (and even beyond).
In this [SPOILER ALERT] summary of the mid-credits scene at the end of "Doctor Strange" we gain clues on what would transpire at the third Thor movie according to Vox.
"Thor tells Strange, who is now entrusted to safeguard Earth from all kinds of dimensional threats, that he's come to Earth to find his father, Odin - no one knows what's happened to Odin since Loki shape-shifted and took his place at the end of 'Thor: The Dark World' and that whole entire complicated story happened where Loki faked his death. But yes, apparently Thor believes he'll find his father on Earth," as stated in the article.
There is an unspoken rule among comic book lore that one should not take accept a character as dead unless the body (corpse) is shown. That did not apply for Odin.
Now the big question: If Odin is alive, where is he and what happened to him?
From the Marvel Cinematic Universe Facebook page, one commenter offered an answer, claiming that the plot of "Thor: Ragnarok" has been revealed. Andrew Miller made a comment in this post.
"They are looking for Odin in NYC (New York City) because when Hela comes to Asgard, she defeats and banishes Odin to Midgard and banishes Thor to another planet where he meets up with Hulk. Banner/Hulk is the champion of the gladiatorial games The Grandmaster (played by Jeff Goldblum) is overseeing (probably for entertainment). Thor and Hulk team up to beat Hela, find Odin on Earth (who lost all his powers to Hela and is basically one of those homeless guys in NYC ranting about the end of the world)."
Miller also clarified some misconceptions. There was an end-credits scene where Thanos already has the Infinity Gauntlet when it was seen in Asgard as part of Odin's collection. This led many to believe that Thanos had already invaded or has been to Asgard.
"So, in conclusion, Thanos already had a left handed gauntlet from somewhere. Odin's gauntlet is a right handed gauntlet, and is still in Asgard. Thanos was not in Asgard during the Age of Ultron scene. He was retrieving it from his own vault," Miller's post stated.
"Thor: Ragnarok" is also expected to reveal the location of one of the Infinity Stones-the soul stone which is suspected to be in Hela's (Cate Blanchett) possession.