Since Hela is the Goddess of Death and since her known powers include life manipulation and because she ruled over the dead in Niflheim, isn't she still alive? I've been reading character pages on Marvel.com, and interestingly, the website mentioned that, unlike other Asgardians, she is immortal. So is she really dead, because the end of Thor: Ragnarok left her fate ambiguous, much like Red Skull's in Captain America: The First Avenger. Yes Asgard was destroyed and it would make sense though if her powers were diminished as a result of Asgard's destruction. But do you think she will appear in A4? And wouldn't it make sense if she was banished to Hel permanently because that is also her homeworld?
Well, based on what the Wiki says, Hela is considered to be deceased. As for my own opinion on this, based on what was shown in the Thor: Ragnarok, she is most likely deceased as the info on Marvel.com can have a tendency of inaccuracies as she was never shown to be immortal in the film. As for her life manipulation powers, we can't be sure if she used them to survive the destruction of Asgard.
As for Hela's appearance in Endgame, I think it is likely if leaked set descriptions are anything to go by. For her being banished to Hel permanently, it could be likely depending on her fate.