Though fans would love to have Robert Downey Jr. and Gwyneth Paltrow portray the role of Tony Stark and Pepper Potts forever, it may be far from possible.

But who could possibly replace them in future installments of the Iron Man franchise?

Though  no rumors indicate that RDJ and Paltrow will turn down the opportunity to return to the roles, it has been reported that the actors have not signed on for "Iron Man 4" -- set to be released in May 2019. In fact, the next two Tony Stark appearances will only be in the next two installments of Marvel's "The Avengers." 

Still, RDJ has not ruled out a future deal for a stand-alone Iron Man movie. He hinted in a recent interview with Entertainment Weekly that he is up for another deal.

"It's down to Kevin [Feige] and Ike [Perlmutter, CEO of Marvel Entertainment] and Disney to come to us with what the proposal is, and that's on us to agree or disagree," RDJ told EW.

"When things are going great, there's a lot of agreement," the actor added. "Right now, this [The Avengers 2] has just been swell, hasn't it? This has been a really good one and it feels good and we're having a good time." 

But in the event that a deal between RDJ and Marvel is not made, Feige said that he believes the Iron Man franchise could still continue even without  RDJ and Paltrow.

"I believe there will be a fourth Iron Man film and a fifth and a sixth and a 10th and a 20th," the Marvel president told U.K.'s OK magazine a few months ago."I see no reason why Tony Stark can't be as evergreen as James Bond. Or Batman, for that matter. Or Spider-man."

Fans are already speculating who could replace RDJ and Paltrow in the successful franchise.

Here are some possible couples fans believe could play the Stark-Potts duo on the big screen:

Colin Farrell and Olga Kurylenko: Farrell is considered to be the top choice of most Iron Man fans for the fourth installment of the series. He is about a decade younger than RDJ, and he could very well portray Tony Start in a lot of future films where the business mogul/superhero is set to appear. On the other hand, Kurylenko was earlier considered for the role of Wonder Woman, and was featured in the 2008 James Bond flick "Quantum of Solace." This means that she could hold her own while being paired with a leading man. At the age of 34, Kurylenko is just four years younger than Farrell who is 38.

James Franco and Emma Stone: A lot of fans see some of Tony Stark's characteristics in Franco. Both are said to be overconfident and self-proclaimed geniuses. Meanwhile, Stone's portrayal of Gwen Stacy in "The Amazing Spider-Man" series makes her a shoo-in for Pepper Pott's role. Both are younger than Farrell and Kurylenko.

Ryan Gosling and Eva Mendes: The real-life couple is also said to take over the role as the Marvel duo. Gosling's 2011 performance in the film "Drive" showed that he can portray roles with an antagonistic side. Both he and Mendes have strong on-screen chemistry together.