The Marvel Cinematic Universe has expanded and there are now more franchises to base a movie on.
As of now, the Marvel Studios movies are wrapping up the trilogies for their primary characters. "Iron Man 3" was shown in 2013, "Captain America: Civil War" will be shown in 2016 on Marvel's "money month" of May and "Thor: Ragnarok" is on November 2017.
The speculations for "Iron Man 4" have never ceased as it seems like Marvel could not afford to let go of Robert Downey, Jr as Tony Stark. Right now, they are casting him in "Civil War" and he is a lock on both "Avengers: Infinity War" movies. Marvel is maximizing Downey/Stark short of giving him another movie.
Which is why What Culture believes that Marvel will eventually cave in, and by 2020, "Iron Man 4" will take one of the movie slots-perhaps the "money slot" in May.
Marvel has established themselves as the big money maker for the pre-summer movie season, grossing a billion dollars three times in that month (Avengers in 2012, Iron Man 3 in 2013 and Age of Ultron in 2015).
They're not taking any chances with "Civil War" in 2016, "Guardians of the Galaxy Vol.2" in 2017 and the "Avengers Infinity War" movies in 2018 and 2019. In short, Marvel wants their biggest blockbusters releasing in May.
If there will be an "Iron Man 4" it will still be Robert Downey, Jr as Tony Stark. A recast for Tony Stark would be unthinkable, and the rumor floating about Ty Simpkins is simply baseless.
While the possibility of "Iron Man 4" is not set in stone, "Guardians of the Galaxy 3" is a safer bet as it lies within the "trilogy rule" and director James Gunn has admitted to Indie Wire that he is working on story ideas for the confirmed GOTG 2 "and beyond that" as early as 2014 right after GOTG 1 released.