Maybe I'm not understanding it, but why would the club sack him? The way I understand it is they're pretty happy for him to finish the year out, they trust him, they're not going to let him make any recruitment decisions for the future, and just get ready for 2020.
The only scenario I see the club willing to sack him, is if Souths sack Seibold and the club just takes a hit to get things started a year earlier, but I don't know, that's a bit of a stretch. I don't think either club wants to pay big money to sack their coaches.
As much as it's all a game now, I just see it as a professional business. Players sign early elsewhere all the time, I wouldn't doubt their commitment to the team for the rest of the season.
Surely the club would understand giving him a swansong would get huge crowds, big marketing opportunities, players doing it for Wayne one last time, NRL fairytale.
I'll be okay if they just swap and get it done a year early, but I'm also happy for him to finish the year.