RTD: I've thought about this for years. When we were making Silence in the Library, you once told me the very last scene ever of doctor who. does it still stand?
MOFFAT: No memory of this. Went back through my emails and found it! This from when we were shooting those shows, I think: In my head (and ONLY in my head, this will probably never appear on screen, or be confirmed in any way) River's not just his wife - she's his widow. somewhere in the terrible future, on a battlefield, the 45th Doctor dies in her arms and makes her the same promise she once made him - it's not over for you, you'll see me again. So River buries her husband and off she goes to have lots of adventures with his younger selves and confuse the hell out of them. Until, of course, she ends up in the data core of the library planet, and realises she'll never seem him again. And then she starts to wonder why anyone would call a moon "Doctor". Ah... Yeah, some version of that could still work. The Doctor worrying that she'll get lonely in the library, and popping his dying mind inside a moon. God, look at those words. I actually typed those words!!!
RTD: I can't believe you didn't remember! I've never forgotten that Doctor Moon thing, it's so clever. Every time i watch that story, I think, it's him, it's The Doctor, and no one knows!.
DWM #551 (2020)