It seems the questions of how Marvel deal with ageing actors, ending contracts and the need to diversify the slate of characters are ones they're consciously seeking to address. The answer seemingly lies in the conceptualisation of the first three Phases as a trilogy (or a saga in more conventional terms), and the Phases beyond that as a whole new world. The impetus - for Kevin Feige at least - is on difference:
"I think there will be a finality to moments of Phase Three, as well as new beginnings, that will mark a different, a very different, a distinctively different, chapter in what will someday be a complete first saga made up of three phases."
So what exactly does that mean?
We already know that Guardians Of The Galaxy 3 is coming, as well as Spider-Man and Doctor Strange sequels (though quite what they'll do with it remains intriguing), and there's a distinct chance we'll see more Ant-Man, more Black Panther, and more Captain Marvel, by virtue of them being the new guys.
But what of the wildcards? What of the new or braver projects that Marvel could tackle that really would make Phase 4 different from what has come before?
12. The Fantastic Four
The issue of the Fantastic Four is probably the biggest elephant in the room for Marvel currently. After their white knight act on Spider-Man, the idea of Kevin Feige leading an expedition to rescue Marvel's first family must be intriguing for fans. Because someone SURELY has to make a Fantastic Four film that works?
The rewards of successfully rebuilding the team would be major. A successful Fantastic Four would mean the opportunity to ease focus away from the Avengers and lots of additional characters. For instance, the Fantastic Four means you can bring in Galactus for one of the only villains bigger than Thanos, and you can push further into the Quantum Realm and multiverse ideas that are already being played with in Phase 3.
Well, they don't own the rights for a start, but regaining them may not be as much of a struggle in light of Josh Trank's disastrous attempt at making a movie for them.
You have to wonder whether there's still an audience for the Four in light of three poor films and their comic book line being sent to the cooler, but Phase 4 is a long time away, and Marvel do know how to build hype for popular old properties.