[Alex]

Thinking about it some more I wonder if the muted audience reaction (at least for people who haven't read the book) to the final events might be because

Spoiler:

the scene before going to the whore-crust where Harry heard Snape and Dumbledore talking made it pretty obvious that Snape was a double agent and therefore the assumption would be that Dumbledore is not really dead in the time honored movie tradition of the fake-bad guy fake-killing the good guy before the real-bad guy can do so.

So their expectation is that the next movie will opened with Gandalf back from the flames and purified into having a much nicer looking beard.

And if that is what really happens (because I have not paid attention to spoilers in great depth then shame on J.K. Rowling.