As of the latest chapters I've read, Megumi is still alive in the manga. Usually, such major character deaths are significant plot points and would be well-publicized if they occurred.
Well, Megumi's story in the manga was full of twists and turns. She had to overcome various obstacles, and there were also some unexpected developments in her relationships with other characters.
Nope, Megumi is alive. The author has chosen to keep Megumi's character alive to continue developing their story and interactions within the manga's world.
The impact on the fandoms is multi - faceted. In the case of the Harry Potter fandom, it can introduce new storylines and character developments that were not possible within the original series. Fans get to see how Harry would react in a completely different universe filled with superheroes. For the Avengers fandom, it adds a touch of the magical and the complex backstories of the Harry Potter world. This can attract new fans to both fandoms. It also encourages creativity as fans try to blend the different powers, cultures, and ethics of the two universes in their own works.