As much as I would love to see time travel trickery or parallel universes I'm wondering if Endgame will deal with the afterlife. I feel the MCU has already hinted at an afterlife. In Dr Strange we see spirits reside in the astral dimension although the spirits seem to disappear after the body dies.. but maybe they move on to a different 'realm' and perhaps the quantum realm could be a link between the physical, astral and afterlife.
If there is any intentional coherency between these details across various films, I would guess the intent is something like this:
1. People have souls / astral bodies / quantum shadows.
2. Doctor Strange showed astral projection of the soul outside the body, but the soul doesn't necessarily have to leave the physical world. It's just invisible to those who can't perceive such things.
3. Physical death severs the connection between the soul and this physical world, so it fades into another layer of reality.
4. The deepest layer of the Quantum Realm ("the Quantum Wasteland") suggests a dimension where thought is reality. Kind of like consciousness creating a world made up of dreams and unconscious thoughts.
5. Perhaps the "wasteland" is the border between the material dimensions with atomic and quantum particles (the conventional laws of physics) and a dimension of
pure thought - as hinted at by The Ancient One.
6. The dimension of thought / consciousness would be a shifting place of memories and imagination, where the astral remnants of physically dead beings reside. Essentially the "afterlife".
Living people's minds contacting this dimension of pure thought would account for visions of people who are truly dead, like Odin appearing to Thor. Thanos' vision of Gamora might not have been inside the Soul Stone as many guessed, but simply Gamora's soul meditating in a place of stillness while thinking of her childhood.
I suspect if resurrections are meant to leave a lasting impact, it might require those returned remembering being dead. Maybe forced resurrection pulls minds back from the thought dimension with them being fully aware of what is happening, or maybe retaining repressed memories of being in the afterlife.
