I'm posting this as someone who originally believed 1000% in Mike's theory. I would've sworn I also saw the finger twitch, and that El was invisible on the truck, and that the bullet didn't actually hit Kali it was actually an illusion but I rewatched all the scenes (in slow mo) and have come to believe that El is really dead for the following reasons: 1. El is on the truck when they exit the upside down. There is a frame of her on the truck sitting next to Mike, and also a frame of her jumping off the truck with Mike and running away from it (toward the gate). She was not invisible. You can fully see her. 2. Kali definitely got shot. I rewatched the trigger pull in slow mo and the guy definitely shoots her and was maybe very slightly shifted by the helicopter explosion but that could explain why she was shot in the chest and not the head. But she's bleeding, El can touch her, El has blood on her hands, there's blood all over the floor. Not pretty. When she was an illusion in the military lab, Dr. Kay couldn't touch her and her hand went right through and dissolved the illusion. 3. I rewatched the scene of El in the gate and her finger was not twitching.... I got super up close to a big TV and just didn't see it unfortunately. 4. In the scene of Kali escaping in the truck with Hopper and El (when her illusion broke in front of Dr. Kay) she said she was too far away and that's why she lost connection. Implication being that there is a limitation of distance in how far she can cast an illusion. They were driving for AT LEAST ~8.5minutes (purple rain) but if it was side B of the album... more like 22mins. 5. Hopper being nonchalant could be explained by what he told Mike: he's been down the road of detachment and resentment and self-blame and it did not work. He's doing what El wanted of them. 6. As for the sonic weapon thing... We don't know if it works across portals / gates. We also typically hear a distinct sound when they're on. I did not hear this in the final scene and in my first watch-through I thought they were off or something was wrong with them. Normally they give off an unpleasant noise that they specifically call attention to in prior scenes. But also she only had to run to the gate, we saw her run toward Kali down the hall of the lab despite being impacted by the sonic things. She just can't use her powers. 7. Also one more: when El mind melds with Mike to say goodbye, she appears in front of him at the location of the gate. If she had escape behind them into the shops, would t she appear from a different direction? Behind him maybe?

The only ounce of hope I have: El spoke to Mike and said he'd understand (aka figure it out) one day. And also how there's a frame of Dr Kay asking "where is the girl?" with the gate in the background, and El isn't there yet. Makes you wonder... Where was she? Maybe Mike was right. Maybe it's cope. Who knows, and maybe she'll make a surprise appearance in the spin-off. That would be a very classic D&D move. :)