'Avengers: Infinity War' spoilers: Robert Downey Jr. teases jam-packed 'Infinity War,' MCU to merge with Marvel TV Universe?

"Iron Man" star Robert Downey, Jr. sent MCU fans into a speculation frenzy earlier this week when he posted a poster for the upcoming "Avengers: Infinity War." The poster, which was revealed to be fan-made, listed the names of the various stars of the Marvel Cinematic Universe (MCU) films, as well as some of the main cast members from Marvel's series on Netflix.

Alongside the names of "Avengers" stars such as Chris Hemsworth, Chris Evans, and Scarlett Johansson appeared those of "Guardians of the Galaxy" cast members Chris Pratt, Zoe Saldana, and Dave Bautista. Also included in the "Avengers: Infinity War" poster were the names of "Daredevil" star Charlie Cox, "Jessica Jones" actress Krysten Ritter, and "Luke Cage" actor Mike Colter. "Agents of S.H.I.E.L.D." cast members Chloe Bennet, Clark Gregg, and Ming-Na Wen were also in it.

Fans initially took the poster, which RDJ shared on social media, as proof that Marvel is uniting the characters in its Cinematic and TV Universes in the highly anticipated "Infinity War."

However, fans later pointed out that the poster is not official and noted that it still listed the two parts of the film even though Marvel Studios recently confirmed that "Infinity War" will no longer be a two-part film.

In July, Marvel announced that the previously titled "Avengers: Infinity War - Part I" will now be known as "Avengers: Infinity War." Meanwhile, "Avengers: Infinity War - Part II," which was supposed to be the back half of "Part I," has been designated "Untitled Avengers."

In a recent interview with Yahoo! Movies, "Infinity War" writers Stephen McFeely and Christopher Markus said that they are many drafts of the film.

"We're on the third draft of movie one and the second draft of movie two," they said. "[We're writing them in tandem] as much as we can. On any given day, you're only working on one but that doesn't mean that next week, you aren't working on the other one. And certainly, notes are coming in and all sorts of production stuff is coming in, like for instance, 'that thing over there is now a window not a door so adjust that.' Or, 'we're not going to this town now, we're going to this town.'"

"Avengers: Infinity War" is slated for a May 4, 2018 release.