Why would Celeborn be dead or believed to be dead? The backstory of them meeting in the First Age in Doriath is only mentioned in the Silmarillion, something the creators of this show have no rights to. So it seems more likely to me that in this version Galadriel and Celeborn haven't met yet.
I find it more likely that Galadriel will at some point travel north from the Southlands/Mordor to the Vales of Anduin and meet Celeborn there, possibly in the very future location of Lorien.
Though I really wonder whether they will show or mention Lorien, what with Lindon already made up to look pretty much exactly like Lorien (a golden woodland, and the leaves of the trees appear to be the same design they used for the Mallorn leaves in the movies) minus the giant trees.
Did you watch Episode 7?
Not a criticism BTW - but based on Galadriel’s dialogue with Theo in this episode, she has met Celeborn as a character, referring to him as her husband, and that the last she saw of him was when he marched off to war, to battle Morgoth during the First Age. And she hasn’t seen him since - and in the context of her and Theo’s conversation, which is regarding Loss of loved ones, it’s fairly clear Galadriel believes he likely died on the battlefield, essentially missing-presumed dead.
So I’m slightly confused to your line of questioning (unless I’m mis-interpreting your post?)