Spoilers ahead for Stranger Things 3. Stranger Things has watched Eleven grow from a powerful, mostly silent young girl into a full-blown teenager slamming doors with her mind, making out with Mike, and embracing her independence — much to Hopper's chagrin. But after losing her powers in Stranger Things 3, Eleven may stay exactly that: a regular teen who's biggest concern is boy drama and nosy parents, not battling monsters from another dimension. For those who got wrapped up in all of the Mind Flayer's chaos, though, let's back up: how did Eleven lose her powers in the first place, and what does that tell us about whether or not they'll come back?
Right before the big Mind Flayer face-off at Starcourt Mall, the D&D crew was horrified when Eleven suddenly collapsed in pain, a small piece of the monster writhing within her now-infected looking leg wound. Eleven summoned a lot of strength to get the tiny creature out, but afterward, she realized that her powers were gone. Three months later, they still hadn't returned, but Mike assured her that they would come back one day.
There isn't an exact answer for why Eleven's powers stopped working, but the Mind Flayer was definitely the catalyst. Will's encounter with a similar creature in the first season has affected him ever since, including giving him those new spidey senses that alert him whenever the Mind Flayer is near. So, perhaps this incident had the opposite effect on Eleven by draining her telekinetic abilities.
The slug creature could have introduced something into her bloodstream that nullified her powers, at least for the foreseeable future. Eleven seems to be doing well with no other negative effects, but another encounter with anything from the Upside Down may reverse whatever happened and restore her abilities — not that she should go seeking out more monsters to try it.
Of course, it's also possible Eleven just overextended herself, and her powers simply need some time to recover. At the end of Season 3, only three months had passed since El's injury, so it's possible that her body is still healing from everything and her powers will slowly return. There's a low vibration that takes place when she tries to use them, which must mean something is still there, right? Though the Upside Down isn't the reason Eleven has powers (that's thanks to the experiments MKUltra scientists performed on her mom, Terry, while she was pregnant) there's always been a connection between her and the dimension, so perhaps it will take her going there or the gate being opened (again) to bring her abilities back.
For now, Eleven is moving away from Hawkins for the first time to live a regular life with the Byers, which will be much easier without any threats to summon her telekinesis. It would be interesting if she uncovered another gate in her new city or ran into another one of her "siblings" from the experiments who could somehow help her rediscover her powers. It's a stretch, but anything can can happen in this series — even Eleven never regaining her powers at all.
But while she may not currently have any otherworldly abilities, El found new power in becoming her own person and getting to experience life as a regular teen. So, if and when her actual powers return, the Mind Flayer and every living creature in the Upside Down better go into hiding because she isn't going to want to lose any of that newfound freedom — or any more of her loved ones.