So this could be the spoiler for the Marvel's upcoming movie Dr. Strange, as the surprise element in the movie has been revealed here.
According to the sources, Marvel Cinematic Universe is planning to add up a surprise role for one of the most daunting Avengers characters in the upcoming Dr. Strange Movie. The Avengers character will play an important part in the movie, though in a cameo.
It's is reported that Tony Stark will show up in the Marvel's Dr. Strange movie, and will ask Dr. Strange to join the Avengers Program. So it will be interesting to see both Dr. Strange and Tony Stark meeting up for the first time.
After the death of Nick Fury,Tony Stark would take the charge of Avengers Program and he is to be the head of the superhero unit. He will considerably look to recruit more superheroes under its wing after losing Rhodey, Vision, and Black Widow for various reasons.
However,the MCU officials are found to be tightlipped regarding this strange development. But as the trend shows, MCU happens to be fond of cameos,as we have already seen Spiderman in the Avengers:Civil War.