Are we looking at this too literally? Isn't the out here more of a meta-commentary in that 'Eleven' might actually be 'Twelve' and that would set up the most of who was actually 'nine' who turns out to be the John Hurt character that some people are already hinting/guessing is a missing version of the Doctor?
I'll go with most of what they throw at us regarding Doctor Who because I love the character so much. But I think this revelation might be a bit hard for me to swallow. So the last two Doctors have just been lying about how many past selves he's had?
OK, so rule one is the Doctor lies (one of Moffat's additions to the character that I really dislike), but it would really change what we know about the character and the show. I'm not sure it'd sit well with me.