Tonight's episode established that "the other dimension" isn't a one way ticket to despair and damnation. Major Briggs ran there to hide and it cost him his head, Cooper wasn't really given a fair choice when he got mixed up with that business with Windom Earle....
but apparently humans can come back from that dimension as we saw with Andy and the long story of James' work partner....
but like a victim of a terrible Trauma, I firmly believe the Cooper most audience members remember and love and so want to see come back just isn't going to come back.
I think like Andy (in the visions that he saw while sitting with the Fireman) The truth was revealed to cooper (that Leland wasn't who actually murdered Laura but rather was the logical instrument to her death) but unlike Andy, who seems to be on a mission, Cooper has been dislodged (no pun intended)
thoughts ?
Coop was sent to the room in limbo by the Arm's doppelganger. Naido flipped the switch so he could escape by taking Dougie's place. Perhaps "the Fireman" rescued Naido & sent her through the portal where Andy & the rest found her.
Fire walk with