(SPOILERS FOR Paradise X: Ragnarok #1 , Loki: Agent of Asgard: Vol. 3: Last Days , Avengers Disassembled: Thor , among other media.)
Avengers: Endgame (2019) is coming up and certain characters are supposedly going to disappear after it ends. For instance Chris Evans’ multi-movie contract is over and he no longer wants to play Captain America. Evans and the other actors have become connected to their respective characters in much the same way Christopher Reeve got connected to Superman. In other words, a lot of movie goers most likely will not easily accept a replacement. So Marvel Studios and Disney have to consider whether to take the risk and recast characters or let them die, retire, or be limited to cameos.
It can easily be said that the human characters would not benefit from recasting with new actors without potentially losing moviegoers. Yet a way exists where the god characters such as Loki, Thor, etc. can possibly be successfully recast. You see, while earlier movies such as Thor: The Dark World (2013) waffle on whether Thor and his ilk are gods, Thor: Ragnarok (2017) states that Thor is a literal god. Which means that he could die and then be reborn after some time. For example Avengers Disassembled: Thor features the Asgardian gods facing their end and essentially dying. A few years later, Thor comes back from death in a rebirth that essentially suggests that belief can revive him and other gods (Thor by J. Michael Straczynski Omnibus ).
There is also the fact that in the comics, Loki is known to change his appearance (Loki: Agent Of Asgard: Vol. 3: Last Days). Not to mention that both Loki: Agent Of Asgard: Vol. 3: Last Days and Paradise X: Ragnarok #1 suggest that tales of gods and belief inform how the gods look and act. In other words, Disney’s new streaming service (Disney+) could see a Loki storyline where a different actor plays Loki and brings back the Asgardians through storytelling. Though this is all speculation and opinion at this point, it could very well be the only way to recast some characters without major backlash from casual moviegoers, or losing the interest of veteran comic fans (who could be sick of reboots and eternally young characters).
Loki: Agent of Asgard #16 (2015) Writing by Al Ewing, Art by Lee Garbett, Coloring by Antonio Fabela, Lettering by Clayton Cowles.