@TheGrammys tweeted earlier today confirming Miley's appearance at the Grammy's.
"Barbra will be introduced by Kris Kristofferson! Kris will also be presenting, along with Miley Cyrus, @ActuallyNPH, & Seth Rogen!"
So it's confirmed and no longer a rumor. Miley Cyrus will not only be attending the Grammy's but also presenting this Sunday feb 13.