Well, there's no definite information available on when the AOT manga will end. It depends on various factors like the story's development and the author's plans.
There is indeed an end credit scene in Toy Story 4. It adds a bit of extra fun and sometimes hints at potential future storylines or gives a final touch to the movie.
The ending of the AOT anime aligns with a particular part of the manga. However, there might be some differences in the presentation and emphasis of certain plot elements.
One end credit scary story could be about a haunted movie theater. After the last credits roll, the janitor hears strange whispers coming from the empty seats. It turns out a ghost of an actor who died during filming haunts the place.