"I think we've given plenty of hints as to who may die - perhaps too many, in that every one of our lead characters is left in a dire, life-threatening situation the month before," executive editor Tom Brevoort told The Associated Press.
The group includes Mr. Fantastic, Invisible Woman, Human Torch and The Thing. The superheroes were created nearly 50 years ago by Stan Lee and Jack Kirby.
The Associated Press contributed to this report.