The impossible has finally happened, with Marvel officially returning Jean Grey's sister Sara to life after being presumed dead for over 30 years. But her return to the X-Men universe brings with it the one mutant superpower with the potential to not only change the team, but the entire reality of Marvel's Earth.
The bombshell has been dropped earlier than fans expected, with Phoenix #12 telling "the secret origin of Sara Grey." But fans already know what Sara's return truly means. Assuming Marvel has the guts to stick to the original plan, that is.
X-Men's Original Plan For Sara Grey's Mutant Power
With Sara Grey seemingly dead and gone, legendary writer Chris Claremont had no reason to keep his original plans for the character to himself. In the decades since, Claremont has offered many insights into the "Dark Phoenix Saga," the death of Jean Grey, and Marvel editorial's desire to (unsurprisingly) bring her back to life as soon as possible. Claremont explained the original plan for a mutant Sara Grey, specifically, on the Jay & Miles X-Plain The X-Men podcast:
"Out of nowhere comes the genesis of X-Factor, and the resurrection of Jean. I actually pointed out to [Editor] Jim Shooter that, aside from the fact that resurrecting Jean totally invalidates everything we did... and essentially tells the readership that nobody dies in comics, and suspense is all bulls***. We were ignoring, what I thought, was a far more interesting and positive alternative. Which was her big sister, Sara."
Not only was it Claremont's wish to have Sara Grey replace his sister Jean on the team, but recruit her to the X-Force roster. Obviously the story would begin with Sara's own mutation confirmed explicitly, gifting her with the mutant ability to activate the X-Gene in a human being. And as a team of mutant-hunting, mutant-seeking, and mutant-saving agents, the ability to 'wake up' a person's previously unknown mutant nature would be invaluable. And explosive.
Sara Grey's Mutation Can Change (or Destroy) The World
a brand new layer to the definition of 'mutant' in its current continuity, is it a coincidence that Sara Grey should be brought back to life now?

As Xavier Leaves the Franchise, X-Men Is Setting Up a New Meaning for the Team's Name
Professor X is heading to space for Imperial, and a forgotten figure from the X-Men’s past might be giving new meaning to the franchise and its name.
If Sara Grey's return means a chance to actually deliver on Claremont's original plan, and tell the "far more interesting" story he intended to, it's worth considering if that will include her planned mutation. Because if Sara Grey arrives for a purpose, with the ability to awaken the X-Gene in one, several, or an unknown number of human beings all at once, the Marvel Universe is about to dramatically change. And if the past holds true, the anti-mutant (or even neutral) communites of the world won't react well to mutants revealed within their ranks.
The next era of X-Men is beginning, so will a person capable of truly 'creating new mutants' on an untold scale be part of this new dawn? Only time will tell. Until we have an answer, Phoenix #11 is available now from Marvel Comics.
Source: Jay & Miles X-Plain The X-Men