I've seen quite a few people theorize that Jinsuke opens the door... Honestly, it would save him from his current situation, but it would also kind of break the character's writing.

By this I mean that Jinsuke is the god-forsaken man, a person who got here just through talent and effort, a bit like Hattori. To give him the door to celestial awakening now would be rather disappointing.

He would have to overcome the wall that is Ishun just with the strength of his humanity.