While Captain America: The Winter Soldier is earning positive buzz for its strong reviews and record-setting box office numbers for the month of April, even beating out last fall’s Thor: The Dark World’s opening, the two Phase 2 sequels come nowhere close to the success of Marvel Studios’ number one hero: Iron Man. Or should we say Robert Downey Jr.?

Sitting only behind its predecessor The Avengers as the biggest comic book film of all-time, Iron Man 3 solidified the armored, high-tech character as Marvel’s most bankable hero in cinemas worldwide. That makes Iron Man 4 a highly desirable (read: inevitable) commodity that Disney-owned Marvel will one day produce. The two questions are when and will Robert Downey Jr. be involved?

The Hollywood superstar – thanks to the Iron Man-powered career revival – can command the highest of salaries in the business and that means he works on the projects he wants to. It’s how he earned a reported $80+ million from The Avengers and at least $50 million for Iron Man 3. That put RDJ and his agents in a nice bargaining spot when they negotiated a contract extension to have him reprise the role of Tony Stark for The Avengers: Age of Ultron and The Avengers 3.

Sadly for Iron Man fans – and the studio – that contract extension didn’t include Iron Man 4. That doesn’t mean Marvel and RDJ can’t work out a deal in the future to have him keep coming back, but such contract talks likely won’t come until around the release of The Avengers 3, likely in 2018. By then, Downey Jr. will be 53, and the actor – when asked about the future of the character post-Avengers – said he doesn’t want to “overstay [his] welcome” with fans and might retire from the character.

Marvel Studios president of production Kevin Feige on the other hand, when asked about the topic, admits that Tony Stark will likely be recast one day, comparing the billionaire industrialist to James Bond. While that may be inevitable, one day, such a thought is a tough pill to swallow for fans. How do you continue the shared universe and timeline and just swap out the most important actor? Is there a story that could lend the character to recasting?

Iron Man 3 co-writer and director Shane Black – and friend of Robert Downey Jr. – hinted that he believed the actor would come back to do Iron Man 4 and 5 one day. Again, another Iron Man movie will be made eventually. And again, it’s a matter of when and with whom. According to an interesting survey handed out by Marvel Studios representatives at certain public screenings of Captain America: The Winter Soldier over the last few days, it could be sooner than we think.

Kristy Puchko at Cinema Blend was at one of these screenings and snapped some photos of the questionnaire. Along with the usual demographic questions, one question asked viewers what Marvel Studios titles they were most excited to see next:

We can only guess that Guardians of the Galaxy isn’t on there because it’s releasing this year as well, but it’s interesting to see Iron Man 4 listed among the given followups (and new property Ant-Man) we know are coming. Captain America 3 of course, just had its release date officially confirmed for May 6, 2016, in response to its successful opening weekend and writers Christopher Markus and Stephen McFeely, and directors Anthony and Joe Russo, were already signed to return and are breaking its story.

Thor 3 doesn’t have a release date yet but it’s a relatively safe bet to release in May 2017 and already has writers in Craig Kyle (Thor: Tales of Asgard) and Christopher Yost (Thor: The Dark World). Or is it? For Phases 1 and 2 of the Marvel Cinematic Universe, Thor solo adventures released before the Captain America titles, but we can now confirm that’s no longer the case come Phase 3. Since Thor 3 has yet to lock down a date, it’s possible it doesn’t come until after The Avengers 3, although the delay in confirmation may have to do with the studio finding the right director for the project since Alan Taylor likely won’t return.

Thor three-quel in 2017 puts into question whether or not Guardians of the Galaxy gets a direct sequel in the next phase. Some rumors claim GOTG is a one-off that could launch spinoffs, so the cosmic-based property adds an interesting spin to the speculation game of what Marvel is going to do next and what they have on that roadmap of films planned until 2028.

What we do know on the Phase 3 front is that each year there are two movies releasing and the first movie of each pair will be a sequel to an established property, with a new IP coming second. That’s why we’re getting Guardians of the Galaxy this year, Ant-Man the following year and in 2017-18 we’re likely getting Doctor Strange (according to Feige’s hinted timeline). As for the unannounced new property (or properties) in between, the common title that continues to surface is The Inhumans, with there being rumors of Black PantherMs. Marvel and another Hulk standalone feature as well. I’d love to see Nova in there since that could serve as a quasi-sequel to Guardians of the Galaxy that bridges it to the familiar Earth-based characters, and it gives Marvel room to essentially deliver Cap, Thor and GOTG followups in Phase 3 while still counting one of them as a “new’ property.

And what we know about future Iron Man films is that it comes down to delivering a unique and interesting story for Tony Stark, one that’s worthy of Robert Downey’s full-time involvement. With The Avengers movies, it’s easier for RDJ since there are more action scenes, and therefore less of him required on set thanks to his CGI armor doing all the work. Jeremy Renner barely ever saw him during production of The Avengers, as an example. With each Iron Man appearance, there also comes the need to introduce more armor suits, and it’s difficult to top there being dozens of them in Iron Man 3 and the biggest one of all being introduced in Age of Ultron. Yes, we’re finally going to see the infamous Hulkbuster armor.

Hulkbuster Armor – The Avengers: Age of Ultron Concept Art

How do you top that in merchandising the Ironclad Avenger? Maybe send him to space to meet up with the Guardians of the Galaxy just like he did in the modern Marvel NOW! books (see: Iron Man goes to space rumors). That, or Stark can become the director of a new and improved S.H.I.E.L.D. organization, which might fit nicely based on the events of Captain America: The Winter Soldier.

Despite uncertainty from cast members Robert Downey Jr., Gwyneth Paltrow and Don Cheadle, Marvel Studios is definitely thinking about Iron Man 4, but if it’s coming, it won’t be until after The Avengers 3. Will RDJ stick with the character through “Phase 4″ or will Marvel Studios need to recast? Could War Machine be put front and center? What about the other key characters whose contracts run out by The Avengers 3 (Chris Evans & Chris Hemsworth)?

There’s only one solution:

More: Marvel Plans Ahead All The Way To 2028

Captain America: The Winter Soldier is now in theaters, Guardians of the Galaxy opens August 1, 2014The Avengers: Age of Ultron on May 1, 2015, Ant-Man on July 17, 2015, and unannounced films for May 6 2016, July 8 2016 and May 5 2017.

Follow Rob on Twitter @rob_keyes for your Marvel movie and TV news!

Source: CB (hat tip Nicholas)