Think I know How They're Bringing Elena back (without Bonnie Dying)...
So if you're caught up we know that Kai is back (OMG)
And in the recent teaser below it's confirmed that Elena has returned somehow!
https://youtu.be/1dezvDso_MI
And in the trailer from this week's episode it's apparent that Kai will have his hand at bringing her back in exchange of him getting out of hell and "brought to life again".
https://youtu.be/JH58nSU9GPM
Soooooo my theory is, since Kai was able to return it's safe to say that anyone in Hell can cross over through the door that was opened when Cade left and Bonnie released that psychic energy after Enzo's death. And as long as Cade does not return to Hell and Bonnie does not close it- that door remains open and hence characters that have died keep slowly coming through (so far we got Kai and maybe the person who kidnapped Stefan.. and I heard David Anders, Elena's dad, is coming back too).
I think if Cade dies then that door remains open permanently and that's why Kai wants to help kill him so that he can be brought to life permanently.
So back to Elena..... the way they can bring her back without killing Bonnie is by killing her. We've been reminded by Cade repeatedly that Elena's soul will go to Hell. It was an Easter Egg! They're going to kill her. She will go to Hell. And then she will be able to come through that "door" and so long as Cade is killed too - she'll stay alive again permanently.
If this is the way it goes I feel like it all circles back and the writers would kinda make sense.
Don't turn your back. Don't look away. And whatever you do, don't Blink. 🏦