Iron Man 4
Robert Downey Jr teases 'Iron Man 4' may not happen. Is 'Captain America: Civil War' end of Iron Man story?Facebook/ Iron Man

"Iron Man 4" is expected to take off only in phase 3 of Marvel Cinematic Universe, which is not before 2019. Clearly, there is nothing concrete about the plot, cast or release date. But one thing that the latest reports have hinted is that the film's story may be inspired by the "Invincible Iron Man" comic series.

The upcoming comic book series is expected to be out in December this year and features Tony Stark, who will be joined by none other than Spider-Man's girlfriend, Mary Jane Watson.

According to Newsrama, Mary Jane aka MJ, who is now Peter Parker's ex, will be joining Tony Stark. The writer of the comic book, Brian Michael Bendis reportedly confirmed that the web-slinger's former wife and Tony already know each other.

"They know each other. She used to live in Avengers Tower. But that's all I'm going to say for now because what kind of relationship they end up having is a big part of what I would like people to buy the book for," Bendis said.

Though Bendis didn't make the nature of the relationship clear, he did hint that it would be something new and interesting. So will they be romantically linked? "What I can tell you is that it is a new territory for both Tony and Mary Jane. And that is pretty exciting to write," he said.

"MJ is a grown-up woman who has been through a lot. She seems like one of those characters that went down certain paths that may not have panned out the way she hoped; and she's ready for a kick-ass second act," Bendis added.

Now, since "Iron Man 4" doesn't have a plot developed yet and that it's taking off only in 2019, there's a huge possibility that the same storyline of "Invincible Iron Man" could be adopted for the film, reported MasterHerald.

The report has clearly speculated that since there's nothing concrete happening on the movie front, the screenwriters of MCU could be picking up from the plot of the upcoming comic series.

Now, whether the speculation comes true, we will know only when an official statement is released or when "Iron Man 4" hits theatres. Till then, all you Robert Downey Jr. fans, get your RDJ fix with "Captain America: Civil War", which is slated to be released on 6, May, 2016.