Harry Potter and the Incredible Unrealistic Expectations of the Audience

I can't help but wonder how much JK Rowling's ideas for the ending of "the Deathly Hallows" were constrained by the percieved expectations of the fan-base. Especially the reality that there are two more movies to release, which maybe nobody will want to go to if they don't like the way the end of the last book turns out.

A book, the ultimate movie spoiler....