Miles Morales is best known for being the hero of Sony’s animated Spider-Man universe. He's set to return as the web-slinger in the upcoming animated film Spider-Man: Across the Spider-verse, which premieres later this year. However, there is a rumor that Morales may be making his way into the Marvel Cinematic Universe soon.

The Marvel Studios Spoilers subreddit is buzzing as a new rumor suggests that Miles Morales will be part of the upcoming Spider-Man 4. The information was shared by well-known Hollywood insider Film Odyssey on Twitter.
"As it's been mentioned, Miles Morales will be in Spider-Man 4," the insider tweets. "He won't be the same age as Peter, he'll be younger. A little bit of time will have passed since Spider-Man: NWH from what I can tell."
As it's been mentioned, Miles Morales will be in Spider-Man 4. He won't be the same age as Peter, he'll be younger. A little bit of time will have passed since Spider-Man: NWH from what I can tell. No word on if Donald Glover will be returning as his uncle, we'll have to see.
— Film Odyssey (@FilmOdysseyMCU) February 3, 2023
Film Odyssey adds, "No word on if Donald Glover will be returning as his uncle, we'll have to see." Glover played Prowler in Spider-Man: Homecoming and is the uncle of Miles Morales.
The rumor of Miles Morales being in Spider-Man 4 gave rise to speculation that the MCU will replace Tom Holland’s Peter Parker. This new fan theory is based on the comic book where Miles Morales becomes Spider-Man after Parker’s demise. Of course, this comic book series is set in a different timeline, so things could go differently in the MCU. Not to mention, it all feels too soon to replace Peter Parker in the MCU.
After Marvel went all out in the last Spider-Man movie, and gathered all three actors who played Spider-Man into one film, the MCU has barely scratched the surface of the potential of Holland in the MCU. Then again, it's unlikely the MCU is going to replace Peter Parker as the web-slinger in the MCU. Tom Holland recently signed a deal to appear in a new MCU trilogy for Spider-Man and will also be part of two other MCU films. In other words, Marvel is contractually obliged to continue the story of Peter Parker for several more years.
If Morales makes his debut in Spider-Man 4, Parker may mentor Morales. The rumors indicate that a long time has passed since the events of Spider-Man: No Way Home. Parker may already be in the later part of his college days and working as a photographer for the Daily Bugle when he meets Morales.
The appearance of Miles Morales in Spider-Man 4 may be a sign that Marvel and Sony intend for their Spider-verse to be merged at some point. Tom Hardy’s Venom also hinted at crossing over to the MCU at the end of No Way Home, with rumors suggesting that Venom will be making his MCU debut in Spider-Man 4.
A good number of Spider-people are also being introduced in the upcoming Spider-Man: Across the Spider-verse and its sequel Beyond the Spider-verse. It is in the realm of possibility that Holland (even Garfield and Maguire) could make an appearance in the animated film.
TLDR; a bunch of Spider-Men are about to show up on the big screen soon.
Speaking of Spider-Man, Donald Glover, the inspiration for Miles Morales, is joining Sony's Spider-Man Universe as the Hypno-Hustler.