A) Sirius is definetely in this one. His role was confirmed, and besides, he dies in this movie. What would happen if they threw that scene out and then during the 6th movie they're all saying "Oh he's dead" that would be really stupid of them.
This movie is taking the same length to come out after GoF as GoF did after PoA.
C) I highly doubt there's going to be much (if any) elf scenes. They threw it out of last movie, and they play a lesser role in this book, which is longer, so that would be pointless.
I CAN'T WAIT!