“Fall” can refer to many things:
- A literal fall, like the one the Fourth Doctor took from the Pharos Project tower that caused his regeneration, or the much longer fall that the Tenth Doctor took in “The End of Time” that didn’t (at least not right away).
- A time of year, i.e. the season containing November.
“The Eleventh” can refer to many things:
- The Eleventh Doctor.
- The eleventh day of a particular month.
- The eleventh month of the year, i.e. November.
- The eleventh element in absolutely any list with more than ten members.
In other words, there are lots of reasons to think “Trenzalore” probably won’t be the site of a regeneration, and very few (based on that phrase alone, anyway) to think that it will be.