Marvel Studios President Kevin Feige, put this question to rest in an wonderful way at the San Diego Comic-Con.
The idea of creating a detailed timeline of the Marvel Cinematic Universe is something highly welcome as of now.
Though Feige's answer seems to imply that some of the title could actually spoil Infinity War, his response also seems to hint that the reason that a Marvel's holding onto the tile is so that they can concentrate on Infinity War. Just before The Avengers was released in 2012, Marvel issued a photo correcting a popular thought thread that suggested Iron Man, Captain America: The First Avenger, The Incredible Hulk, Iron Man 2 and The Avengers all took place in the same year.
I think some of that has been blown out of proportion. As he's said previously, Feige stated that none of the films are dated unless there's a specific reference, and reiterated that Marvel's official timeline isn't based on years, but is rather centered around Tony Stark announcing that he was Iron Man.
Given the scope of the film, everyone is obviously very hyped-up for the trailer, especially for those who can not wait to see their favorite Marvel Cinematic Universe characters all meet-up together. In a few words, not very well. Speaking to Screen Rant, Feige was quizzed on the spoiler-ish nature of the title, and was asked whether we'd have to wait until Infinity War for it to finally be unveiled.
Feige didn't reveal when said timeline would be published, but with phase three of the MCU drawing to a close next year with Avengers: Infinity War, that might be a natural break point.
Avengers: Infinity War premieres May 4, 2018, while Avengers 4 hits cinemas the year after on May 3, 2019.
So, does that mean The Avengers happened the same year as President Barack Obama's inauguration and Jersey Shore was at its peak?
This is a major teaser coming from the head of Marvel indicating that the superheroine was out there in space during the time that Avengers were being formed on Earth and even before Iron Man came into existence.