It's a given that movies based on Marvel characters are going to have a post-credits scene, and usually it's one that teases either a sequel or the next movie in the Marvel Cinematic Universe. Well, the same goes for Venom, which has two post-credits scenes: one that hints at the plot of a potential sequel and one that teases an entirely different movie.
While Venom is a movie based on Marvel comics, it is not part of the Marvel Cinematic Universe (MCU) as it was produced by Columbia Pictures in association with Marvel Entertainment and distributed by Sony rather than being produced by Marvel Pictures and distributed by Walt Disney Studios Motion Pictures like the films in the MCU. There is some crossover between Sony and Marvel/Disney when it comes to the use of Spider-Man, but even though Venom originated in the Amazing Spider-Man comics, the new movie exists outside of the MCU.
This is an important distinction when it comes to the post-credit scenes, because they do not tease an upcoming MCU movie as would have certainly been the case had this one been a part of the MCU, not just a separate Marvel character movie.
Major Venom spoilers ahead.
So, the first credits scene. This one comes mid-credits and shows what Eddie Brock and symbiote Venom are up to directly following the end of the movie. One of the final scenes of the movie shows Eddie telling his ex- fiancée, Anne, that he landed a big new interview. The mid-credits scene shows the start of that interview. Eddie/Venom head to San Quentin prison, and Eddie tells Venom that "this is a me thing", as opposed to something that involves both of them. Upon entering a maximum security cell, we see a man writing "Welcome Eddie" in his blood on the wall. Soon, it's clear to comics fans who this is by his bright red hair: the serial killer Cletus Kasady, played by Woody Harrelson. If there is a second Venom movie, it will surely show Kasady becoming the villain Carnage after merging with his own symbiote. (Also, it will become a "we thing" for Eddie/Venom.)
As for the second end credits scene, this one is a preview for Spider-Man: Into the Spider-Verse, an upcoming animated movie. Similar to Venom, Into the Spider-Verse will be in association with Marvel and distributed by Sony. The film is about the different Spider-people that exist (and Spider-Ham!) and focus on Miles Morales' introduction to the Spider-Verse. There had been rumors about the idea of Tom Hardy voicing Venom in the movie, but that hasn't been confirmed.
Of course, with Venom coming out on Oct. 5, the Into the Spider-Verse preview from the movie is not available online yet, but there have been other trailers (such as the one above) released in advance of its December 14 debut.
It's certain that Into the Spider-Verse will hit theaters soon, but as for whether Venom will be back for a sequel that will include Carnage, the jury's still out, and so far, things aren't looking great.