I think there will be a reason for Cardan to go with Jude (after she comes back to Elfhame) to the mortal world and like it. Then end up together there.
Based on the cover of queen of nothing, the blood crown will break so either there won't be a king or it won't be the same. I think Cardan knows that there is war brewing that's why he took Balekin's death as an excuse to banish Jude-protect her.
I think Nicasia or Locke are going to die