Of course Moffat had to give us something to chew on....

"On the Fields of Trensimore, on the fall of the eleventh, when no living creature can speak falsely or fail to answer, a question will be asked. A question that must never ever be answered." - Maldovar


There are a lot of theories on this one but lets be honest, most of them suck.


Moffat is often quite literal but no one in new Who has ever directly referred to the regeneration number of The Doctor. Is that somthing the characters can really know? Thats why I don't think this quote can be taken to mean 11ths death/regeneration.  Maybe that will be a factor or result, double entendre for us viewers, but there must be some other meaning to it. 


Given that the question is "Doctor who?' I think we do have to consider that River might be learning the doctor's name, its quite literal but it is Moffat.