The name Robert Downey Jr. is often considered to be synonymous with Iron Man, but that pairing could come to a grinding halt if Marvel chooses to oust Tony Stark from Iron Man 4.

With Downey only signed on for the next two Avengers outings, the fate of the Iron Man franchise is still up in the air. However, if Iron Man 4 was to be put into production (sometime post-Phase 3 if the studio wants Downey to be contractually obliged to do Avengers 3), there is a chance that Tony Stark could be replaced by Arno Stark, according to Classicalite.

Who is Arno? There are two versions of his story, the first of which makes Arno the biological nephew of Tony Stark that grows up to become Iron Man 2020. A more recently Arno storyline (Iron Man Vol. 5, #12) claims that he is the biological son of Howard Stark and Maria Stark. Genetically modified while in the womb, a "genetic clock" would have caused Arno to die early if Howard did create a serum that would let him live. Dependent on life support, Arno was not introduced to his new adopted brother, Tony.

With Downey's increasing age and high cost, Marvel Studios could use this plot as a way to keep Iron Man going without its star. Marvel Studio's president of production, Kevin Feige, previously stated that he saw no reason why Iron Man could not be replaced.

"I believe there will be a fourth Iron Man film and a fifth and a sixth and a 10th and a 20th," Feige said, according to Entertainment Weekly. "I see no reason why Tony Stark can't be as evergreen as James Bond."

For now, viewers can look forward to seeing the "billionaire, genius, playboy, philanthropist" in The Avengers: Age Of Ultron, which will hit theaters on May 1, 2015. Click the video below to see a teaser trailer.