[Scarilian]

In terms of your idea... splitting the second movie into 3 would just cause tons of confusion - especially when the Thanos story alone is going to take them the whole of Guardians of the Galaxy to explain.

Ant Man is in Phase 3 - which essentially means Ultron will be the main villain in the third Avengers film.

Pretty much this sort of thing;

Film; Main Villain - Who it is setting up for future films

Avengers; Loki - setting up Thanos
Iron Man 3; Mandarin - setting up Captain America/AIM
Thor - The Dark World; Malekith - setting up Thanos
Captain America - The Winter Soldier; Winter Soldier - setting up AIM
Guardians of the Galaxy; Drax (Scared of Thanos, later joins the Guardians) - setting up Thanos
Fantastic Four Reboot; Skrull - setting up Negative zone
Avengers 2; Thanos - (Possible death of Tony Stark, Hawkeye, Black Widow) setting up Ant Man
Ant Man; Radioactive man - Setting up AIM/Ultron
Black Widow; Prequel - setting up Avengers - Cameo Hawkeye
Hawkeye; Prequel - setting up Avengers - Cameo Black Widow
Thor 3; Surtur - setting up Doctor Strange
Guardians of the Galaxy 2;
Fantastic four 2; Annihlus - setting up Doctor Doom and Doctor Strange
Doctor Strange; Mephista (Working for Baron Mondo) - setting up Baron Mondo
Captain America 3; Baron Zemo + Arnim Zola - setting up Ultron
Avengers 3; Ultron
Ant Man 2; AIM/M.O.D.O.K - Setting up M.O.D.O.K
Doctor Strange 2; Baron Mondo - setting up Dormammu

In terms of timelines;
Avengers; May 2014
Avengers 2; November 2015
Avengers 3; May 2019