I've heard this a lot over the last few months/years, especially with the dominance of Twilight. People are just sick to death of vampires.
But ask people who devour vampire books if they are sick of them and they will tell you "Please sir, may I have another." Vampire books are their own sub-genre with a loyal following. There will ALWAYS be a market for vampire books. Buffy didn't go off the air because people were sick of the show. It went off the air because Joss Whedon had told his story and wanted to move on.
People who are sick of vampire books are typically not the ones who read them in the first place. If people are sick of something, it may be poorly written vampire books, such as Twilight.
Are you sick of vampire books?