Jack Kline being God doesn't really last long in my head. He fixes everything Chuck fucked up and goes home to a very alive Castiel and a very alive Dean and a very excited and alive Miracle. Sam and Eileen just moved out of the bunker and they basically share custody of Jack so he visits them every few weeks and stays for a few days.
Bonus points for Jack finally being able to live out all of his neurodivergent traits because in my head Jack is definitely autistic.
Gabriel would totally mess with Jack in heaven. Doesn't matter that Jack is God now. (As a matter of fact that makes it even more fun for him.)
Gabriel would tell Jack that The Chipmunk Christmas Song is the Winchester's favorite Christmas song and Jack would be like "Oh. I didn't know that. Thank you, dear Uncle." and would go ahead and randomly make that song play in the bunker during the holiday season to make his Dads happy. Gabriel would just sit back and watch Sam and Dean lose their minds because Jack is God and therefore they literally can't stop the song from playing at the most random times.
Can you imagine Team Free Will celebrating Christmas after Jack becomes God. Jack would definitely be there which would lead to Castiel spending the last few weeks leading up to Christmas desperately searching for a gift for Jack because WHAT THE HELL WOULD GOD WANT FOR CHRISTMAS ANYWAY?
