The CW has released an official description of the episode
7.16 – “Out With The Old“. Airs: Friday, March 16th, 2012 at 9/8c

After a ballerina is found dead from dancing herself to death, Sam (Jared Padalecki) and Dean (Jensen Ackles) look into the case and discover the ballet slippers she wore were cursed. When Dean accidentally touches the shoes the power of the curse starts to take hold of him.

Written by: Robert Singer & Jenny Klein, Directed by: John F. Showalter

Here is a special episode preview, this preview contains clips from multiple episodes, so at the end of the preview, you will see Castiel (Misha Collins), but Cass is actually in episode 7.17.
So don’t get too excited yet … Ah hell – Who am I kidding, go nuts!

Source: The CW