Thor: Ragnarok doesn't arrive until November 2017 "“ so there is still plenty of time until then. As a matter of fact, Kevin Feige and all the powers that be haven't even decided on a writer or a director for the project.

However, he did say that Thor: Ragnarok will be one of the most important events of Phase III. And how couldn't it be? Ragnarok is, after all, the end of days "“ the war that will see the death of all the Asgardians (or somewhere along these lines, in any way).

Midgard before Asgard

In Age of Ultron, Thor's vision (which was the most awesome, in our opinion, second only to the one of Hulk) saw Heimdall and other Asgardians in Hel, blaming the God of Thunder for their fate. And it can be said so, because he did leave Asgard in favor of Midgard, thus leaving his people in the hands of fate (or Loki, about whom he didn't know he killed Odin).

And there is also one more scene from the trailers which hinted at Thor: Ragnarok and didn't make it into the actual film "“ that mysterious woman in the pond where Thor catches a glimpse of the Infinity Stones! Come on, do you really believe that it was a scene of no importance? If it was so, then they wouldn't have shown it.

Presenting such a character in a setting so strange surely had to make some sense. And, as said in here, that woman might just be Death or even Hella.