Iron Man 3 continues to dominate the box office, as Marvel’s latest film starring Robert Downey Jr. joins the $1 billion box office club today.

Iron Man 3 has joined a fairly exclusive club today, along with the 15 other films which have grossed over $1 billion at the box office. The film was released on April 26 internationally, and May 3 in the U.S., and within three weeks of its release has crossed the $1 billion dollar mark. Disney has their sixth billion dollar movie on their hands, the most for one studio.

After 23 days in theaters, Iron Man 3 is set to pass $300 million domestically today. With a foreign box office total of nearly $700 million – this will end up giving it an estimated worldwide total of over $1 billion.

Iron Man 3 also broke multiple box office records on the way to its first billion, becoming the second biggest opening weekend ever with $174 million worldwide, just behind Marvel’s The Avengers, which holds the #1 rank with $207 million. It took the place which Harry Potter and the Deathly Hallows – Part 2 had held previously, which had pulled in $169 million and the most recent film on the list, The Dark Knight Rises – which pulled in $160 million on its opening weekend.

Iron Man 3 should see somewhat of a dip soon as fans start heading to see Star Trek Into Darkness, which had its release date pushed up one day to Thursday, May 16.

Our guess is that the third Iron Man film will end up pulling in an estimated $1.1 billion worldwide – putting it around the #6 spot for all-time box office grosses. The previous film in the franchise, Iron Man 2, pulled in $623 million worldwide, which has now been dwarfed by Iron Man 3. This is most likely due, in no small part, to the monstrous success of Marvel’s The Avengers, and also because this was the first Iron Man film that was promoted by Disney, which certainly has shown its benefits.

There’s been much debate as to whether Marvel will make an Iron Man 4, or whether Robert Downey Jr. would even be willing to continue to play Tony Stark in solo Iron Man films, but we’re certain he’ll be putting the suit back on for The Avengers 2, which will hit theaters May 1, 2015. There’s simply too much money on the table for him not to return for The Avengers sequel. Downey reportedly pulled in $50 million for The Avengers, and now that his contract with Marvel is up and with Iron Man 3 breaking box office records, the amount of leverage he has is probably the most that Hollywood has ever seen.

With Iron Man 3 being such a massive financial success for Marvel/Disney, despite mixed reviews (currently holding one of the lower scores for a Marvel film on Rotten Tomatoes with a 78%), we’re certain Disney is throwing as much money as they can stomach at Robert Downey Jr. to do Iron Man 4. He’s reportedly in negotiations right now for Avengers 2, and while there has been no official word in terms of Downey’s involvement, we’re certain he will be joining The Avengers 2 cast (who are having their own problems renegotiating their contracts with Marvel).

There is no doubt though, Iron Man 3 is a massive financial success for Marvel and Disney, but the foreign markets continue to bring in the majority of the box office. More than 70% of Iron Man 3’s box office numbers have come from foreign markets, which means we’ll continue to see Robert Downey Jr. and the rest of Marvel’s cast and crew headed overseas to promote their films as Thor: The Dark World, Captain America: The Winter Soldier, and Guardians of the Galaxy head to theaters in the next few years.

If Robert Downey Jr. does decide to do another solo film, or Marvel decides to replace him (blasphemy), Iron Man 4’s release date would be during Marvel’s Phase 3, which should begin hitting theaters in 2015-16.