I've been wondering about how Sam and Dean will react to Chuck being God, but I hadn't thought much about how Chuck/God would react to Sam and Dean, now that he has been revealed.
In the preview/clip, Chuck comes across as someone who is tired. He seems to play the role of the annoyed/frustrated younger sibling, detailing how awful it is to live with a sibling who always tells you what to do. Obvious nod to Sam, and admonishment to Dean. (Dean didn't look to enthusiastic.) Later in the conversation, when Dean tells Chuck they have tried everything, Chuck says he's always had faith in them (looks at Sam) even when they didn't return the favor (pointed look at Dean).
So it should be interesting to see how this is handled. I think God likes them both, but he's always favored Sam.
It does leave the door open for Dean/Darkness/Amara and Sam/God/Chuck parallels/showdown. The show is constantly coming back to family and siblings. Could it be that the resulting issues - Micheal vs. Lucifer, Cain vs. Abel, Dean vs. Sam - are all reflecting of the initial sibling rivalry between God and the Darkness? Is this inherent in God's creations because he subconsciously kept going back to his own issue? That he is defeated because no matter what he creates it always seems to go back to that dynamic? Maybe he hopes that Sam and Dean will break that cycle. Don't know. Food for thought.
(I doubt it'll go fully in that directions. Just couldn't help but notice.)
For the record, I think Sam will be in awe of God/Chuck, like he had been in awe of the angels, and how he was always a prayerful person. Inverted in how he was the rebellious son.
I think Dean will be either angry or emotional, as he had always questioned God. Inverted in how he was the dutiful son.
Curious to see what happens. Also, I want to see the eventual reaction of Castiel, who is clearly God's favorite angel.