So who dies?

No the epilogue shows Nathan and Elena as an older couple - with a child.
It's clear that they are done with the crazy adventures.
Instead returned to journalism / archaeology without risking their lives.
They do have a very nice beach-house though!

Extremely unlikely Nathan will be the main character in another Uncharted game.

That's not how Naughty Dog works if they say it's done than it's done. They did the same with Jak and Daxter, I know people are so used to how most companies just turn out sequels because hey free money but Naughty Dog really has no issues leaving it on the table.

If they wanted to, they could do it.

We see a (gratuitous, in my humble opinion) epilogue starring Nate and Elena's daughter and dog, but the kid is in her early teens and we don't know how much time passed between the Libertalia gig and her birth. So there's a sizeable gap in Nate and Elena's history that could accommodate another outing or two. Ain't no law that says they couldn't see some action while the little one's hanging out with a nanny, or maybe even visiting uncle Sully and uncle Sam.

There were also some earlier gaps - between the events of Drake's Fortune and Among Thieves and before Drake's Deception - when Nathan and Elena were together and then apart again. Plenty of room and reason for those stories to be told. Maybe even an opportunity for some of Elena's solo adventures - after all, especially once she'd moved from video documentaries to conflict journalism and investigative reporting, she'd have a few tales worth telling and probably her share of action, too.

Would be nice to see Chloe and Charlie, again, too.

I'd really love to see that. Wish Naughty Dog and Sony were paying attention.

But, in my version of the pipe-dream, Amy Hennig and her team come back to the table. I don't care what the reviewers say. I really miss Nate's self-deprecating wit, and Elena's ironic wit, and Sully's ribald wit.

That was a lotta wit, and I miss it all. A Thief's End was practically witless.