Warning: major spoilers follow for Avengers: Endgame.
Here are our two biggest questions at the conclusion of Avengers: Endgame: Is Thanos really dead, and will he stay dead? For the purposes of the Marvel Cinematic Universe, the answer to both parts is a resounding "YAAAAAS," especially given the disbandment of the current Avengers and the numerous other properties on the horizon for the studio.
But when we consider how the gemstones work, the Mad Titan's death could prove to be temporary, assuming the Avengers fail to immediately destroy the six Infinity Stones. That is to say, we learn in Endgame that anyone in possession of the Infinity Gauntlet and its gems can use the device's power. Thanos hints at this in the opening of the film when he explains the importance of destroying the gems to avoid reuse. So, as long as the stones remain in existence, Thanos has a slim chance of getting out alive. But how?
"As the stones remain in existence, Thanos has a slim chance of getting out alive."
We theorize that when Tony Stark snaps his fingers to obliterate Thanos, Stark doesn't permanently destroy the Mad Titan but merely absorbs him into the Soul Stone. In the Infinity War comic series, this stone has the power to control life and death by capturing a person's essence and storing it in the Soulworld, which exists within the gem itself. The souls captured by the stone remain trapped, unless the owner decides to set them free.
Of course, Earth's mightiest heroes do not intend to release Thanos. But if we dig deeper into the Marvel comics, specifically the Silver Surfer series volume three, we learn that the Silver Surfer escapes the Soul Gem and returns to reality with the help of a genetically modified superhuman named Adam Warlock. Warlock cultivates the ability to travel back and forth between the soul and surface realms by finding a way to communicate with the gem's consciousness. Or to put it plainly, Warlock convinces the stone to share the secret of its power. He then uses his connection to the gem to reincarnate himself — and others like Gamora — into the bodies of recently deceased humans so he can rejoin the land of the living.
Thanos is a persuasive guy with a surprisingly sensitive soul (for a villain). Theoretically, he could learn to do something similar during his captivity in the stone and return to wreak havoc on the Avengers. We think this is possible because Thanos already has an affinity with the Soul Stone. Remember, at the end of Avengers: Infinity War, in the moments after the snap felt around the globe, we see Thanos materialize in an orange-hued dimension that appears to be the Soulworld. He encounters a young Gamora there, and she asks him what his victory cost. He answers, "Everything," and we can tell that he is genuinely saddened about sacrificing his daughter to gain the Soul Stone. This moment clearly shows that Thanos can enter and return from the gem.
Granted, this ability comes when he is the bearer of all six Infinity Stones and in control of their power, but who is to say that the Soul Stone's consciousness won't remember this connection — as well as his heartfelt sorrow — and continue to allow Thanos to travel between worlds even after he's lost control of the stones?
We'll be the first to admit that we're stretching the laws of logic here. After all, the magic and lore associated with the comic book version of the Infinity Gauntlet and its stones don't always jibe with the films, but much of what we've seen on screen has the potential to give Thanos a rebirth.
Obviously, Marvel has no plans to bring Thanos back any time soon, but Avengers: Endgame is so devilishly good that we can't help dream up ways to instigate another showdown.