MCU Phase 4: 10 Massive Stories Marvel Could Adapt Next
3. Annihilation
We already know that James Gunn wanted to use Annihilus as a villain in a Guardians Of The Galaxy movie (ideally at least), and with the Guardians director moving into a creative advisory role for Phase 4's cosmic stories, there may be an opportunity for him to get his way. Provided, again, that Marvel and Fox could do a deal to bring the character to the MCU, obviously.
Annihilation would allow Gunn the kind of huge cosmic-focused event that he'll no doubt be looking for, and it would be the kind of story that could easily be launched with Guardians Vol 3, which Gunn has confirmed will be the launch point for Phase 4.
Starting it with a literal bang and destroying Xandar would be a great move for impact too, and it would allow for the long-mooted introduction of Nova (as the rest of his Corps is wiped out by Annihilus), leading to a stand-alone for him after Guardians, perhaps a Captain Marvel in space movie and then an event release taking on Annihilus. It wouldn't necessarily have to be a seven movie Phase, but it would be a great way to explore the Marvel cosmos.