So I did some digging and found out what happened at the post ending-sequence with the overhead voice, aka God. It seems that God says to Kim that he has a proposal for him. Possibility of a 2nd season and a happy ending for WayKim? I hope so at least. I hate sad endings in dramas, I want the fairy tale happily ever after since you get so much sadness from real life already.
I have to say that I do live a cameo in a show and this cameo was top notch. The OST gets stuck in your head after a while.