She won't top those sales with BTW.
Her sales didn't come from fans (see my last few tweets

), they came from the general public. And the general public bought her stuff because the media couldn't stop talking about this new girl who was like this generation's Madonna.
Now that the novelty has worn off (and I don't mean this in a bad way, it's inevitable that it'll wear off), there won't be as much "WHO IS THIS LADY GAGA???" coverage with BTW.
She'll open bigger, though.