Okay so after listening to the recording a bunch of times I heard some new things that were not originally heard and I think I’m on to something. First of all the person that is screaming is 100% Will, but I don’t think it’s Steve he warning I think it’s Mike. The first thing Will screams never sounded like “Steve” to me and on closer listen it really sounds like he’s yelling “MIKE”. This would make a lot of sense given other leaks and theories we have, Holly goes missing so Mike and Will team up to look for her just like how Johnathon teamed up with Nancy. This would explain why they’re in the upside down together (I’m asumming they’re shooting in the upside down rn). Also Will is 100% getting possessed and I think he’s fighting Mike in this scene, he’s telling Mike to run so he doesn’t hurt him but Mike doesn’t listen and things escalate. This would make sense with the (not confirmed) leak of Mike getting badly hurt and going to the hospital, I mean the fight sounds pretty brutal and there’s also a clip of Finn talking about have fake blood in his mouth and he started saying “there’s a lot-“ but cuts himself off when answering about not being a stranger to gruesome stuff.
This does however make Will kissing Mikes forehead a little sad, he probably feels so bad for hurting Mike. I feel like Wills gonna try to distance himself from Mike in fear he’s gonna hurt him again (praying I’m wrong I really want more byler scenes 😭)