Answers: 1
Accepted answer: no
Accepted answer: no
Spoilers:
In the end, Elizabeth and Booker realize that Booker becomes Comstock at the baptism turning point, but in an alternate reality remains the Booker Dewitt we know in the story. It is in the latter reality (Booker Dewitt's) that Booker births Anna. This event in the sequence would have to have been after the baptism turning point, and thus with Booker dying, he could not have had Anna in that reality, he would not have become Comstock in the alternate one, and he could not have joined with the Lutece's and would not have founded Columbia. So, in the end, shouldn't Booker, Comstock, Anna (Elizabeth), Columbia itself, and any other realities connected to them not exist past the baptism?