The Marvel Cinematic universe will eventually expand to 67 characters who are likely to appear in Avengers Infinity War movies, and this set off a kind of competition among every major character wanting to get more screen time before it becomes outdated. The studio executives said it in a panel “We thought the most compelling way to start off Infinity war would be to have the Avengers fight off each other when the greatest threat they will ever face shows up”. [Referring to Civil War]
The classic comic-book story in Phase 3 is unlikely to change much where Thanos first finds out where all the mind gems are, then he will assemble all the gems and create an all-powerful Infinity gauntlet, cause a worldwide catastrophe.In Marvel comics, they are in the possession of all the elders of the universe, it’s different in cinematic universe as Vision has a mind gem, but he clearly isn’t an elder of the universe. In Avengers 4, Team Ironman and Team Cap will bury their differences & unite to save the world. There will be a crossover of Avengers and Guardians of the Galaxy to come to the aid of the Avengers against Mad Titan. Spiderman will definitely be there with a new suit (a new upgradedIron-Spidey suit to be manufactured by Stark Industries).
What is then the timeline of Spiderman Homecoming in Marvel Phase 3? In the new international trailer released recently, the Marvel studios have made the timeline pretty clear. There is a scene of Tony Stark and Peter Parker walking in the new Avengers facility as the Avengers tower is too damaged and unusable. Another scene features Peter Parker in the old hoody outfit fighting bad guys before he gets a sleek tech suit. Hence, the homecoming story shall begin 6 months from the time of Avengers: Age of Ultron and will continue to build MCU post events of the Civil war.