Speculation ahead
This whole Civil War thing is very interesting, and I now expect something very different, though ultimately ending with the Infinity Gauntlet story still. All the reports we've been hearing leads me to believe we'll be seeing a New Avengers movie for Avengers 3, which I'd personally title Marvel's The Avengers: Disassembled.
Captain America 3 will likely leave the concept of the Avengers in ruin, which would leave Tony Stark with another tainted ruined legacy. So in one final attempt to redeem himself, he hires a new team of Avengers, leaving them to operate as the worlds 'New Avengers'. Those would be Ant-Man, Wasp, Falcon, Scarlet Witch, Quicksilver, Vision, Mockingbird, and also Captain Marvel/Black Panther dependant on their involvement in Phase 3. Ideally I'd have Hank Pym lead the team as the guy taking charge at the base kind of deal, assuming he survives. A team along these lines would then take on the logical villains following Civil War - the Masters of Evil. A team of villains assembled essentially as a Hydra kill-squad, lead by Baron Helmut Zemo, approved by the Military and Government due to some hidden Hydra influence. Zemo would have his own plan - to return the Red Skull using an Infinity Stone. This then ties the story to the overall MCU, and follows on from Cap with the Hydra influence. Ideally my Masters would consist of Zemo, Loki, Abomination, Crossbones, Absorbing Man, Madame Hydra, and maybe Bullseye. The movie would then play out however it'd play out, but the end would be the link to Avengers 4 - Thanos being revealed to be working with the Red Skull, who knew Hydra would attempt to find him, and Loki revealed to be working with Zemo in an attempt to redeem himself in Thanos' eyes. Thanos then claims the last stone and leaves, but the Masters are defeated - the New Avengers still 'win', but Thanos now has all the stones.
Then you lead straight into Marvel's The Avengers: Infinity War, where the Guardians arrive on Earth and the original Avengers are forced to assemble once more to finally work together to save the universe, despite their differences, and would be where the big three (or four, counting Hulk) would reconcile and become Avengers once more. This concludes the overall story arc so far, and allows the repercussions of Civil War to be resolves as well.