The following story contains MASSIVE spoilers for Thor: Ragnarok. Seriously, stop reading now if you do not want to know how this movie ends.
By the end of Taika Waititi's new Marvel movie, Thor: Ragnarok, the end of Asgard -- as predicted in the title of the film -- has come to pass. Knowing it's the only way to stop Hela (Cate Blanchett), Loki (Tom Hiddleston) and Thor (Chris Hemsworth) resurrect Surtur and unleash him on Asgard. Thor has come to realize that "Asgard" really consists of the people from his home, not the place, itself. With that in mind, Thor piles all of the surviving Asgardians aboard a ship, and blasts off with them into the cosmos, setting a course for Earth.
It's during the mid-credit sequence, however, where things get really interesting. Let's talk about what happens, and what we think it means for Avengers: Infinity War and beyond.
Only one of the two Thor: Ragnarok mid-credits sequences seems to have a greater effect on the MCU, as a whole. (The second one is a cute Jeff Goldblum comedic bit.) In the first sequence, Thor and Loki are discussing the plan to head back to Earth. Loki questions whether it's really a good idea for Thor to bring HIM back to Earth, seeing as how one of the last times we saw him there, he was opening up a portal in the sky, through which aliens were swooping down and destroying Manhattan.
Before the step brothers can finish their conversation, though, a ship that's significantly larger than Thor's current craft hovers over them. We get a wide-angle shot of the massive ship... and then nothing.
So, our "educated guess" is that it's Thanos' ship. Why would Thanos be in that area? I think that we have the answer to that, but it means we have to read into the footage that was shown at D23 and San Diego Comic-Con... the Avengers: Infinity War trailer that has yet to see the light of day. I'm going to break that down on the next page, just in case people who haven't seen that trailer yet want to be protected from what is shown.