For years, it seemed like it would never happen. The X-Men, a hugely important piece of Marvel Comics canon, were shut out of the Marvel Cinematic Universe for as long as their movie rights were owned by 21st Century Fox, which continued to grind out new films featuring the team long after the continuity of the series fell apart and quality plummeted.

But with the Disney-Fox merger around the corner, fans no longer have to make peace with the idea that Cyclops will never shake hands with Spider-Man. It’s a new era for the X-Men, just in time for the MCU’s Phase Four.

While we’re celebrating the victory for Marvel Studios, though, we may want to keep in mind that there’s no guarantee yet that the upcoming MCU films integrating the X-Men will be any good. Changing studios solves some of the problems inherent to the Fox films -- the muddied timeline, the uneven cast, the setting that differs from the real world only by way of mutants existing -- but it will create others. Impressive as Marvel Studios has been so far, we know better than to think they can do no wrong.

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It’s also not true to say that Fox’s X-Men movies have done no right. The first one, released in 2000, was a crucial building block for the superhero genre in cinema. Altogether, they’ve contributed their share of high-stakes conflict, underlying themes of prejudice and the specialty of the genre: Stuff that looks cool. Those successes belong to those movies, and Marvel Studios would be making a huge mistake in trying to replicate them.

So, when a new cast of actors take up the roles of the first few mutant characters to appear in the MCU, what we’ll be looking for is how differently their introduction is approached. Keeping the mythology intact will be a tall order, since by that point dozens of MCU movies will have gone by with nary a mention of the mutants among us. But the element of uncertainty around Phase Four means that a rule-changing reset might be in the works already, so anything goes.

If people with mutant abilities start popping up in a world already accustomed to superheroes, this may finally be the chance for Professor X to guide us through it by traveling the world and recruiting students for his School for Gifted Youngsters. Not only would that bring in a diverse international team to work with, but it would be a refreshingly unique way to blend the newcomers into the existing canon while still honoring the source material.

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A more long term problem is that the newcomers aren’t newcomers. The bank of Marvel’s mutant characters (and their enemies and allies) to draw from is large, but not infinite, and most of them have been picked over for Fox’s movies and TV shows. The minor characters remaining might very well be enough to support a franchise on their own, except that fans expect certain beloved characters to be present, no matter how many times we’ve already seen them and no matter how much we may have complained about characters being continuously rebooted.

Hugh Jackman has now played Wolverine in eight movies over 17 years. You know who he is, and let’s give him due credit; he’s been a blessing. He’s also unambiguously done with the role now, which may lead fans to ask if there can be an X-Men without Wolverine. The better question is if there can be a Wolverine without Jackman, and the answer is yes. Remember the short, hairy, uncouth berserker who first appeared in the comics in the 70s? A generation of movie fans have never met him, and they don’t need another superhero heartthrob to take his place.

Logan isn’t the only character who could be successfully recycled with a makeover that stays true to the comics rather than previous film or TV incarnations. Storm can finally be tall and regal, torn between her natural leadership ability and her bond with nature. Rogue can have access to a variety of plot-based reasons to permanently absorb some additional superpowers, even if she never meets Carol Danvers. With the MCU’s grasp of special effects, there shouldn’t be any obstacle to designing a furry Nightcrawler, or putting a miniature dragon alien onto Kitty’s shoulder.

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Of course, some of the characters have already been overused disproportionate to their relative importance in the series. In some cases, it may be better to just leave them out, at least for the first few years. Others may be necessary, but can’t be improved by changing Fox’s formula. Frankly, there will never be a better casting for Charles Xavier than Patrick Stewart, and the MCU is just going to have to work around that.

Classic X-Men themes still open for exploration in film go beyond individual characters, and even specific events. Fox’s movies put a big emphasis on the outcast status of mutants and the dangers of discrimination against them, but there was never anything like X-Factor, the team conceived by the founding X-Men to find and protect young mutants while pretending to hunt them for the sake of the public eye. X-Factor’s ultimate failure as its ruse backfired would make great fodder for a movie or two. So would Excalibur, one of several teams that were formed by “survivors” of the original X-Men after the others were presumed dead (pssst, they really weren’t).

If nothing else, it’s high time for the X-Men to head into space. Some of their greatest adventures have pitted them against hostile alien races like the Brood, acquired alien love interests like Lilandra or crossed over with spacefaring hero teams like the Starjammers. For an Earth-based institution, the X-Men have a strong tie to the cosmic Marvel Universe, and they’ve always seemed a little unfinished without it.

This is an exciting time for the MCU, and the anticipation of the big changes to come is part of the fun. Whatever Marvel Studios chooses to do with their newly acquired characters is going to be worth watching, but if they manage to pull off the balancing act it takes to make the X-Men new again, it could be much, much more than that.