Jack is still kicking around somewhere and has all of God's powers. Heaven obviously still exists so all remaining angles must as well. There is the empty where Cass is stuck so if the spawn of lucifer can be born grow to adulthood in a blink and become all powerful in a fraction of Sam and Dean's life I'm sure something could happen, Chuck was god so probably vengeful and maybe had some safety net or didn't destroy all other universes or Chuck sold Supernatural to Disney and Disney ruined the end so we were duped. 🤔🤷‍♂