I'm not sure why people who played the game before release were so confused - to me it seems pretty clear that at the very end - Elizabeth is killing Comstock booker simultaneously in all of the universes he inhabits at the point of his baptism - thereby negating his creation at all, thus the post-credits sequence is just MC-booker living his life without the intervention of Comstock-booker i.e with Anna.
Am I missing something? The only thing I'm unsure on is the motivation of the luteces.
I love the scene where Booker is indignant at Elizabeth's suggestion that he doesn't have any free will and proclaims that he can go wherever he wants to - but the player is physically stuck and can only move in the direction that the bridge forms in, and indeed you can see future versions of booker and elizabeth following the bridge all around you. It's the kind of metaphor you can only execute in this medium, this effectively at least.
If Booker from baptism forward ceases to exist then he couldn't be around to have Anna since Booker doesn't have Anna until
after he turns down baptism and lives his life in NYC.
Elizabeth drowns Booker thus Comstock/Booker ceases to exist past the point of Baptism, but Booker still exists prior to that and Booker will still reach that point in time, he'll either accept or deny, probability. Since it's a choice when he makes one, another universe will always spawn in which he makes the other.
The other thing that could happen is every time Booker from any timeline reach that particular point they're either suddenly downed by a girl he doesn't know (this girl being Elizabeth/Anna) or he suddenly ceases to exist.
A divide by zero situation can makes sense if you understand what happens when you divide by zero
I don't know guys, do you hear Anna crying in the post credit scene? i don't think she's there.
btw. awesome theory DoctorWho you should send this to Ken Levine and his team.
You never hear Anna cry through out the game, not really the best indicator that she's there or not. Though if Booker is there as Booker and not Comstock at that point in time then by extension Anna would have to be there since Booker goes on to have a child.