User blog comment:Mlgrsd/Who could that be?/@comment-26982641-20170515220718/@comment-25589722-20170516034141

My guess is Bobby :)

First I thought it could be Michael but judging by the person's body shape it doesn't really fit JDM and certainly not Jake Abel (Adam/Michael)... Jim Beaver on the other hand is more fitting and Cass sure could be surprised about him being there .. whatever this "there" may be... Also it seems like there is somebody rising from the dead (similar like Dean in 4x01 and Adam in 5x18) and the hand that is shown also doesn't fit to JDM but more to Jim Beaver.

My theory (and really just theory) is that Bobby was thrown into The Empty after the things he did in 10x17 Inside Man for some sort of punishment like you said... And in the finale Cass was send to The Empty by Lucifer or maybe he was even killed and we finally get to find out that ... well... angels go there after they're killed or something like that... and there he comes across Bobby who fought his way to the main portal thing (those 4 stones that you can see in the video) and yeah… again just a theory ;)