I literally think it's impossible unless something bad happens to her reputation in the meantime. I think the lowest she could possibly go is 600k or so, which is still amazing.
I don't like what she did with Red, using all the pop songs as singles considering the deepness of the other stuff, but you know, she's smart enough to know that she needs that to skyrocket her sales, and her pop stuff is still better than the usual, so I give her credit for that.