There's a theory making the rounds that another famous group of Marvel superbeings could show up in The Avengers: Age of Ultron. Warning: potential spoilers ahead.
As everyone knows, the characters of Quicksilver and his twin sister, Scarlet Witch, will appear in The Avengers: Age of Ultron, played respectively by Aaron Taylor-Johnson and Elizabeth Olsen. In the comics, the siblings are mutants and the offspring of Magneto, but since 20th Century Fox owns the actual concept of "mutants" as they pertain to the Marvel Universe (because the studio owns the rights to the X-Men property), Marvel Studios itself cannot use that term, nor can it make any reference to Magneto.
So what is the solution? According to Unleash The Fanboy, a source says that Marvel will introduce the twins as Inhumans, members of the race of human offshoots enhanced by experimentation performed thousands of years ago on them by the alien race known as the Kree.
With the siblings positioned as Inhumans, that will leave the door open for more of the Inhuman Royal Family to show up in Age Of Ultron, possibly during the course of the film or in one of Marvel's famous post-credits sequences.
There have been reports that Marvel wants to launch an Inhumans movie, and this is one surefire way to introduce the species, while also making them the replacement for "mutants" in the cinematic Marvel Universe. And since we've already got a Kree villain coming in Guardians of the Galaxy in the form of Ronan the Accuser (Lee Pace), there is groundwork already being laid for the Inhumans' origins -- which may get even more fleshed out in The Avengers: Age of Ultron.
Do you think that we might see the Inhumans in Age of Ultron? Does using them as the stand-in for mutants make sense for the expanding Marvel Cinematic Universe?