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.