Game Of Thrones Season 7 Finale: Predicting Who Lives & Who Dies
16. Varys

Where He'll Be
With Jon and Dany at the Dragonpit, presumably getting lots of daggers thrown at him from Cersei's eyes. Or revealing that he's working with her, if you go in for that sort of rumour.
Verdict: Dies
He's pretty expendable, and he's not really had a great deal to do this season other than threaten Melisandre and learn that he's probably going to die. If there is to be a battle at the Dragonpit, he's unlikely to be able to do a great deal to protect himself, and since he's survived this far by aligning himself with those who can protect him, we might well see the end of the Spider.
It'll be a shame, but he has very little to do when the action shifts to the white army next season, so that might well be the sound of his death knell.
15. Missandei

Where She'll Be
At Dany's side in the Dragonpit (unless the theory that Dany doesn't go initially is true). She'll be the one talking on behalf of Dany presumably.
Verdict: Lives (Just about)
Missandei is a fairly neutral figure, so her death wouldn't really have that much of an impact. That might count against her as she could be killed off as collateral damage in the pit, but it feels more likely that she'll be a casualty without actually dying.
She might be injured, but she's probably too pure a character to be killed. Unless Grey Worm survives, in which case she might well be killed off to give him some more rage to play with.