"Iron Man" fans have some good news coming their way. According to latest reports, director Shane Black has confirmed that the fourth instalment of the very successful series by Marvel Studios is very much happening, and Robert Downey Jr. is definitely reprising his role as Tony Stark.

While speculations were running wild about Downey's return as Stark, Black was 100% certain that he would be the man to don the Iron Man suit and that "Iron Man 4" will soon get rolling, reports Master Herald.

The website reported that the film has been delayed because the production house was in negotiations with the actor, who requested for an increase in his already high talent fee ($50 million).

The report also pointed out that Marvel may not mind the hike and would agree to the actor's price, given that "Iron Man 3" was a huge success for the studio (earning $1.22 billion at the box office).

Now finally, it looks like after all those rumours and delays, Robert Downey Jr. will be back for the fourth installment. But there are various other plot/cast rumours that have kept fans really curious.

One of the wildest rumours is that Harley Kenner (Ty Simpkins), the boy genius who met Tony Stark in "Iron Man 3" and helped him track down the Mandarin, will replace Downey Jr. to take over the superhero's job.

According to Movie news Guide, Tony would retire in "Iron Man 4", which might be set in future where Harley will be all grown up to become the perfect successor. The website also pointed out that the casting change could also be a build up to the future films.

Another rumour suggested that "Iron Man 4" may release after "Marvel Phase 3" in 2019. There have also been reports that the extended Marvel Cinematic Universe (MCU) may come to an end after "Phase 3".

And finally, the most important rumour hints that the plot could revolve around the terrorist organisation Ten Rings. If you remember, Ten Rings was the reason why the Iron Man suit was created.

The terrorist group is run by Mandarin, which kidnapped Tony Stark in "Iron Man". The reference was reportedly made in "Ant-Man" when a businessman, who goes to Pym Technologies, reveals a neck tattoo — a symbol of the Mandarin.

Now which of these rumours is true will be known 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.