Six Forgotten Warriors Chapter 5: The Price of Heroism - S5-E6
Plot hole: This series is in the same continuity as the other Marvel animated series from around the same time - X-Men, The Incredible Hulk, Iron Man, and Fantastic Four - by virtue of each aforementioned show crossing over with at least one of the others. This episode, which originally aired on October 17, 1997, establishes that Captain America had spent the last 50 years locked in another dimension with Red Skull, and the episode ends with he and Red Skull once again becoming trapped in the aforementioned dimension. However, the final episode of Fantastic Four, entitled "Doomsday," which originally aired on February 24, 1996, features a cameo by Captain America in the present day, attempting to stop a rampaging Dr. Doom.
Answer: Yes. Many things that would have been in the sixth season would have had Norman Osborne returning from limbo and reclaiming the title of the Green Goblin, Richard Fisk, the son of "The Kingpin" Wilson Fisk would return as a crime lord known as "The Rose", Ghost Rider would have appeared to help Spider-Man stop Dormammu from returning to Earth and Madame Web and Spider-Man would rescue Mary Jane from limbo.