Having said that, I strongly feel that, if such a time actually does come, Buffy will settle down in her white picket fence surrounded cottage with someone totally human, someone capable of giving her children and a relatively happy life (too happy, and she would become bored quickly) someone with whom she can grow old and watch their children grow.
Honestly, I don't think that Buffy's the kind of person who ends up with somebody. It's just not her life, not her story.
No one. I think Joss will kill her off before he ever decides to make a definite choice in this argument that we've been having for 15 years. It's entirely too much fun for him.
Personally, I kinda don't understand the appeal of a settle down/happily ever after ending. Do people seriously want the apex predator of the occult world to become a soccer mom in some boring suburbia?
And of course, Buffy's romantic relationships are much more of a focus than those of the world's greatest detective ( I...think, please correct me if I'm spewing bullshit, I'm not much into Batman ) but still, she's just as much of a warrior, just as much of a superhero.
If Buffy ends how Fray describes it (and thats only if) then we know that Buffy isn't going to settle down- she's going to go out in some blaze-of-glory apocalypse with those she cares about around her/falling with her. Who gets to be blazing along with her is the question.
And that's the way it should be. I like the idea of maybe a Scooby surviving or something, but Buffy shouldn't fade away- that's never been how a slayer does things.
The final battle at the end of Season 8 was supposed to be the battle described in the "Fray" series, but something changed the outcome (maybe Spike arriving with his bug ship, but that's just a guess) thus creating an anomaly that would ultimately result in Willow going dark and still being alive in Fray's time.
Whether that is right or not, the way that the battle was described in "Fray" it seems to me like the story line has gone past the time when it was supposed to happen. Course, that mostly depends on your definition of "the early part of the Twenty First Century" really is. I would define it as sometime within the first 10 years, so we're past the time.