But in all seriousness, I feel like we'll have so many Avengers by Phase 4 that Marvel will hopefully keep them as two separate teams.
Just looking at Infinity War Part 1 being rumored to kill off the current cast and have a new team assemble to fight Thanos, it's obvious that Marvel has plenty of toys to play with.
My guess is that this will be Infinity War Part 1's roster after Thanos kills half the universe including everyone in Avengers Tower.
Captain America ---> Winter Soldier
Iron Man ---> War Machine
Thor ---> Doctor Strange
Hulk ---> Luke Cage
Black Widow ---> Mockingbird
Hawkeye ---> Falcon
Quicksilver and Scarlet Witch ---> Ant-Man and the Wasp
Nick Fury ---> Spider-Man (as the guy who brings the new team together)
Vision is the only remaining member since he wasn't, "alive" to begin with.
Infinity War Part 2
Everybody from Age of Ultron and Infinity War Part 1 returns for Infinity War Part 2 but with Daredevil, Quake, Black Panther, Jessica Jones, Deathlok, Iron Fist and Captain Marvel all joining the Avengers to fight the Magus.
Then Inhumans happens and we get a new team to round out Phase 3.
Phase 4 should be a breather until the final film which is a massive punch to the gut. It would also feature more numerous Spider-Man films since Sony wants to make them and bump the schedule up to four films a year since Sony will be financing Spider-Man along with Venom, Silver Sable and Black Cat films. Films released in Q1 would be riskier ventures which wouldn't be scared of getting an R-rating, may introduce new characters or be somehow unconventional but would also rely on a lower budget. Sony films would also get the Q4 slot since there is no way that Marvel will let them hog their summer money.
Phase 4 should end with Kang defeated but as things return to normal, Norman Osborn is now the Director of SHIELD. Phase 5 should be dark Reign with Norman Osborn as the big bad and culminate with Siege.