I believe Dexlyn/Pythium has kept us waiting in previous turns before.
I suggest leave his nation for the next 2 turns, to see if anyone can sub or Dexlyn to turn up. If neither happens, turn him AI. Its better to have the AI play him than no one at all.
I had another player drop out who was my neighbour in another MP and turn AI. The AI put up a far better fight than the previous player. It was very annoying but amusing also.
If anyone goes away or wants to drop out, its only fair to let the host know. Rather than have us all hanging on like this.