To all the people saying “the Russo brothers and Markus & McFeely are smart, they wouldn’t kill Loki in such a stupid way and leave all these hints that he might still be alive”:

• They’re not that smart. Civil War was terrible; The Winter Soldier wasn’t as great as everyone says it was; and hello, have you seen what they did with Infinity War? Even aside from Loki’s stupid death, I mean. Thanos’s “sympathetic” Malthusian worldview? Fridging Gamora for Quill’s AND Thanos’s Manpain™? Our heroes deciding that a whole bunch of Wakandans can die so that Vision doesn’t have to because “we don’t trade lives” (right…)?
• Markus & McFeely wrote Thor: The Dark World, which had a really weak main plot and not that much involvement from Loki until Joss Whedon was brought in as a script doctor and added more for reshoots.
• Markus & McFeely originally intended to kill Loki permanently in TDW but Feige made an executive decision to bring him back because of his popularity with fans at the time. His mainstream popularity has (I think) waned since then (partly due to the deliberate diminution and demeaning of his character in Ragnarok).
• I wouldn’t be surprised if M&M wanted to finish the job they started in TDW. They fridged Frigga to bring Thor and Loki together through Manpain; they had every intention of fridging Loki permanently for the sake of Thor’s Manpain.