Also, I don't think phase 4 will be as long as phase 3. The reason why phase 3 is so long, is because I think Marvel is serious about making some big changes to the Avengers lineup.
Possible Phase 4 lineup:
2020:
Doctor Strange 2(Or Inhumans)
Spider-Man 2(Tentative on any deal made with Sony)
GOTG 3
2021:
Black Panther 2
Ant-Man and Wasp 2
Captain Marvel 2
2022:
Avengers 4
New Movie
New Movie
Hmm...
In phase 1 they showed 4 "new" faces (5 with the Avengers) in six movies.
In phase 2 they showed 2 new faces, and had to keep the other faces going - with the same amount of movies.
In phase 3 they had to continue 5 fanchises (6 with Iron Man, but they did not make a fourth movie) within 6 (!!) movies.
So they had to expand the phase...
And i think, they thought "NOW is the time to see, what is possible".
They wanted to make a Doctor Strange movie, the fans asked for Black Panther and Captain Marvel. And the Inhumans could give them a whole new franchise with many possiblities - after ther success of the Guardians maybe even no big risk for Marvel.
On top, they got the Spiderman franchise back later...
What i mean - if they would have stayed with just 6 movies, they could not show ONE new franchise at all.
Therefore, they had to expand...
Line up changes are just THREE of them, Inhumans is a different case.
So, i do not see any "now it is time for a change"...
I think it will (in the future) be more like "now we will have more team-up movies" AND maybe we see a very special phase 4 - maybe with a story within itself. So "everybody is (almost) in every movie"...
Furthermore, i think we will see the
Illuminatis AND
F4!
I do not see a "Antman w/ Wasp 2"...
And i still think, that we maybe will see in november 2019 (or even 2018) a fourth movie.
Still the question is, if 2020 is still phase 3 or already phase 4??
I am sure, that we will see in 2020:
1. Guardians of the Galaxy 3
2. Spiderman 2
And i still think, that they will announce "Doctor Strange 2" for November 2019 (if the first movie is a success), we will see a new property in November 2020 - f.e. Fantastic Four.
Or something old like Iron Man, Captain America or Thor. (but they will not show a Iron Man or Captain America movie in November -> would then be GotG 3)
As they did not announce the movies NOW, that means - in my view - that they KNOW what they want to show, but they have to wait for some decisions.
"Success"=Doctor Strange, Spiderman or "contract"=Iron Man, Fantastic Four
Otherwise, they would have announced all three movies already...
But that also means - in my view - that they do not show us a new franchise (other than F4).
If 2020 is already phase 4, we have to continue the following franchises:
1.Doctor Strange
2.Guardians of the Galaxy
3.Black Panther
4.Captain Marvel
5.Inhumans
6.Avengers
7.Spiderman
And i am sure, that we will see at least
8.Iron Man
9.Captain America
Futhermore
10.Fantastic 4
11.Illuminatis
The Illuminatis would also fix the problem with "to many heroes for the Avengers", as Black Panther, Iron Man or Doctor Strange would be a part of the group.
And would fix the "Iron Man/RDJ problem", as they want to show him surely again in "some movies" - f.e. also in "Spiderman 1" (in 2017).
And i am sure, that we see a movie, where HULK is the bad guy - maybe against the Illuminatis, better against the Avengers!
Maybe again in a two-parter...
I do not see it, that they "just do 9 movies (over 3 years)" in phase 4.
PS
I know, that your opinion is, that we will not see Iron Man, Captain America and Thor around after phase 3.
That will not happen - but i am also not sure, if they will do a fourth movie with them.
But they will use them in other movies for sure - RDJ is their draw. Evans wants to continue... "Winter Soldier" was big, "Civil War" will be big...
They will still need them...
I think, we will see something BIG in phase 4. A story throughout the whole phase, with changing line-ups/team-ups for almost every movie, with the final in May 2023 or/and 2024!