How many "copycat" submissions do you see? Have you ever seen a compelling "copycat" submission?
Do you mean plagiarized? Or simply an idea that's hot?
I've never gotten a plagiarized manuscript.
I've gotten Harry Potter-esque submissions and Twilight-ish submissions. Sometimes they've been good, but not right for my company.
Generally, if a book has hit it big, the trend is over by the time the copycats start showing up.