User blog comment:Tommy,Klaus&Kol2012+/How to Kill a Levithan/@comment-168.16.130.206-20120227233017

and since Meg is returning with Cas(according to spoilers/photos), maybe Crowley sends her to help Cas and the boys find some ancient Leviathan-killing weapon, and maybe the Leviathans' deaths will unleash next season's Big Bad somehow.