It's all been building to this: Avengers: Infinity War, a two part movie event happening in 2018 and 2019. It's the culmination of the first three Phases of the Marvel Cinematic Universe, and will tie up the story of the Infinity Stones and Thanos. It's going to be huge.
Here's what we know: A while ago I reported to you that not all of the Avengers would be in Avengers 3 (ie, Infinity War Part 1) and everything we heard today at Marvel's big Phase Three event backs that up: with Captain America: Civil War it seems likely Cap will no longer be wielding the shield, and Thor: Ragnarok makes me think we may not have a Thor to kick around anymore (at least for a little while). Intriguingly there are two films between the two halves of Infinity War: Captain Marvel and The Inhumans. Kevin Feige confirmed that Infinity War is very much space-based, so Captain Marvel fits right in. The Inhumans? They're often Earthbound, but not always, and Thanos is related to them. It all fits in.
As for the rest of the Marvel universe: while Feige acknowledged that the Netflix shows and Agents of SHIELD take place in the same contiguous universe, he was not quite so forthcoming on whether The Defenders would get mixed up in the Infinity War. It all depends on which way Marvel goes with this story; the studio seems happy to use the titles of comic stories without adapting much of the meat. In the Infinity War comic series the heroes of the Marvel Universe battle evil versions of themselves, something that could be redundant after the big events of Captain America: Civil War.
Avengers: Infinity War Part II will end Phase Three on May 3rd, 2019. What comes next?