Warning: SPOILERS for House/Powers of X
The role of mutants in Marvel's Universe has been forever changed by the X-Men relaunch, told in House of X and Powers of X. But it seems one key detail about a major X-Men leader may have been misunderstood by fans... if not missed completely.
Readers can be forgiven, since there are only so many twists, reveals, and breaking of continuity that can be processed at one time. And even in the realm of comic book reboots, Jonathan Hickman's X-Men reboot is one to remember. An event that makes mutants gods of the Marvel Universe is one thing. But it's also the event that returned every key X-Men hero to life with a fresh start. No hero or heroine may be more deserving of that second chance than Jean Grey--but readers apparently still missed the true meaning of her character arc within this X-Men relaunch. Which could mean big things about her future in this brave, new, mutant world.
When the first artwork and cover images for the House of X and Powers of X series began their release to the public, fans made note of Cyclops's new X-Men uniform, Wolverine's return to his classic brown and yellow--and the return of Jean Grey's green dress. Officially, her "supersuit" first worn as Marvel Girl in the early days of Marvel's X-Men. But compared to the suit she had previously been wearing in the pages of X-Men: Red, some observers were... less than impressed to see Jean back in her '60s-era dress and boots. A look that is, admittedly, uncommon in modern superhero comics.
But there is more to Jean's costume change than fans apparently grasped. That's according to Hickman himself, who fielded fans' most burning questions via AiPT. When the costume change for Jean was brought up in regards to the controversy it sparked as a step backward in gender representations, and if she would be sticking with it for the foreseeable future, Hickman revealed it to be one story element that most readers apparently missed completely:
I’m not going to lie, this one has been disappointing.
I was pretty sure everyone would figure this out as soon as House of X #1 hit the stands. And while I’m not going to spoil the story for you, I will say go back and look at the most famous time she put this costume back on. That should help. And to answer the other part of your question directly, Dauterman is actually doing some Jean stuff now and she’s wearing a version of one of her newer suits (but colored green and gold, as all Jean costumes should be).
The storyline Hickman is referring to is almost certainly Jean Grey's famous Dark Phoenix Saga--just not the chapter most point to. After Charles Xavier succeeded in psychically 'blocking' the Phoenix Force from taking control of Jean, the X-Men were arrested by the Shi'ar Empire. For Jean's crimes (committed as the Dark Phoenix persona) she was sentenced to death, before her friends stepped forward to fight a duel for her freedom. With the fight of her life ahead of her, and with no costume on hand, she made a choice that spoke volumes for her character journey to that point.
The return to her classic costume takes place in Uncanny X-Men #137, and her lover Cyclops is the first to witness it. When he asks Jean to explain the old wardrobe, Jean explains she isn't entirely sure herself: "I'm not sure--Nostalgia? Pride? I started as Marvel Girl, and that's how I'll finish it."
The simplest reading of Hickman's words on the issue is that his intention was to return Jean to her old costume--her first uniform, and her original vision of a mutant hero--because that is how she was viewing the future ahead of her on the Mutant nation of Krakoa. A new day for mutants everywhere, but the same one she had believed in before her life (like so many other X-Men) spun out of control. Not to mention she was also preparing for another fight of her life, dying on the mission to destroy the Sentinels before they could be created.
For those who prefer a more sinister theory, Jean Grey donned the green dress when she believed she had returned to her true, heroic self... before the Dark Phoenix eventually returned and took over once again. So it could also be possible that Hickman's intention was to inject that same level of uncertainty. Given how much continuity this X-Men relaunch willingly ignores, erases, or throws out completely, it's impossible to say what Jean Grey's connection to the Phoenix Force currently is. Or more importantly, how her physical form being regrown in 'peak' condition could impact that very relationship.
It has also been theorized that Jean has been reverted to an earlier version of herself, thanks to the mental side of the mutant resurrection/cloning procedure. While that process creates an empty body of a given mutant, it is the mental scan--recorded and re-uploaded by Charles Xavier--that makes them the person they used to be. When Jean appeared in her original Marvel Girl appearance, and was told she was "safe" by a smiling Xavier in House of X #1, it was unclear just what they were truly speaking to. In the context of Jean's costume and the last time she wore it, it's still possible Xavier gave Jean Grey an earlier mind, oblivious to the dangers still lying inside of her. And considering how disturbing this new Charles Xavier really is, we're not putting anything past him.
Whatever the truth, it sounds like it will inform her next character arcs in the Dawn of X and beyond. Even if the actual dress doesn't stay for the entire journey. Fans can read the official credits and plot synopsis for X-Men #1, beginning the new line of Marvel's X-Men comics on October 16th, 2019.