Eddie died, we see his corpse,

Hes gone, that’s it

Hes dead, dead dead. the Duffer brothers said hes dead. not coming back dead 🧟

He's dead, he's not coming back, sadly

He isn’t coming back.

I think there is a strong possibility we will see him in some form or fashion in ST5.

After all, six months ago (talking about Billy), people were saying "he's gone, that's it, he's dead -- we will not see him in ST4".

Then, we saw Billy in ST4.

So, in some form, whether a vision or something else, I think we will see Eddie again.

It's far-fetched, but we know that the Upside Down is frozen in time from the day El opened the gate. We also know that Will survived a week there without any food or, crucially, drinkable water. What if, while people can be killed in the Upside Down, they won't die of natural causes and if they are killed by the Demogorgon or Vecna, they are effectively frozen at the moment of their deaths. So, even if months or years have passed in the Rightside Up since their deaths, their body has only just died. El was able to bring Max back to life after she was dead for a minute. If Eddie's body remains in the same state it was in at the moment of his death, perhaps El can also bring him back to life.

More likely, Eddie will appear as a vision if Vecna chooses to torment Dustin, or he could continue to exist within Vecna, and join Max (and Barb) in fighting him from within.

@ReganX This is the best theory yet, and one I could get behind if worst came to worst.