In the original comic books, the Ragnarok storyline was all about getting Thor off the map for the Civil War event of 2005.
Mysteriously enough, at the same time, also before Civil War, Hulk was shipped off planet, via rocket ship, to land on an alien world where he would eventually rise to become ruler. The title of THAT event was Planet Hulk.
I guess that the films decided that they were going to do two of them at the same time.
For those people who remember, when we last saw Loki, he was taking over Asgard disguised as Odin. And here, we see Hela, queen of Hel trashing Asgard. This version may or may not be related to Loki, like the original myths, but it's a really long story or Marvel doing whatever they like with mythology.
So, Hela trashes Asgard. Thor becomes a gladiator on an alien world but by Jeff Goldblum, and runs into Hulk. There will be smashing.
I suspect that the three act structure of this one will be-- Asgard is toast at the 40 minute mark, Thor, Banner and Loki are able to get away from the alien gladiator world by the end of act 2, and act three will open with Strange consulting/
Yes, Cumberbatch is confirmed to be in this movie as Doctor Strange. In fact, if you look at the IMDB page, the cast list starts with Loki, then Strange, Idris Elba's Heimdall, Cate Blanchett's Hela, and THEN, Chris Hemsworth. He's getting fifth billing and he's the title character? Oy. Obviously, this will not be in the credits for the film, they'll have a different arrangement, but still....
SPECULATION: As I said before, just going off of the title, this will enable Thanos to get his hands on the Tesseract / Cosmic Cube from Avengers. Or, as I said,
This means that Ragnarok will either have Thanos attacking Asgard, or will have Thanos in a final, post-credit scene in which he goes through the wreckage of Asgard, coming up with the gauntlet, and probably the Tesseract.
With Thor going to other planets in this one, will Marvel take this opportunity to has him run into the Guardians of the Galaxy? I would, if only to bring them more into the fold.
Also, right now, we have five Infinity gems accounted for, there's one outstanding. When last we looked, Dr. Strange has one, Vision has one (putting two on Earth), The Collector has one, Asgard has one, and the Nova corps has one.
Guardians 2 and Ragnarok are perhaps the best opportunity for Thanos to get three out of six -- but there is Captain Marvel and two more Avengers films that should provide ample opportunity. At the very least, I expect to see the final infinity gem revealed this year. (Yes, I also said that it's possible it could show up in Wakanda. If it doesn't show up in the main MCU films this year, that's the only option left)
But we'll see.
The Love at First Bite series.