My very first thought - Eleven has died. Or something drastic has happened to her. Any other thoughts? This could be big, guys

By the way, what is your source, @PresidentSmith609 ?

I thought of the "Eleven has died" angle - but then I thought that such a huge plot development in the end would be something they would keep carefully under wraps.....but messing with us would be something that the Duffers would do. @Fisher Fan

Right, exactly. It was my first thought, because that's what it's supposed to look like if they really wanted to mess with us. But I doubt it will happen, considering the weight of her character. However, that doesn't rule out a grave injury or something else, which might explain why it's Hopper and Mike, and not Jonathan and Mike (should something have happened to Will, for example).

@Fisher Fan - Think of all the other characters who might die, whose deaths would emotionally impact Mike - Hopper could be consoling Mike in regard to any of those deaths.

Or, the Duffers are completely playing us and none of those characters are going to die.

That's true - it may have been released, as it was assumed we'd infer it was about Eleven, when it really could be about anyone close to their hearts. I guess we'll just have to wait and see!