The Australian will join Doyle, Holder, Sedgmen and Watt to make up the 2017 QBE Insurance Australian FIM Speedway GP team.
Maciej Janowski took the victory from championship leader Jason Doyle and Matej Zagar.
Double world champion Tai Woffinden heads to Cardiff in search of his third title.
Team GB head into the Speedway World Cup Final with confidence after easy Event 1 win.
Jason Doyle is currently suffering with three broken bones in his foot.
Team captain Emil Sayfutdinov leads Russia to race off victory, seeing them through to the World Cup final.