No, Dambuster are just providing support. THQ Nordic's financial reports list Sumo as the lead developer with support from Dambuster. A bit of poking around reveals Dambuster seem to be handling the motion/performance capture stuff since they have their own facilities. However, Dead Island 2 is not Dambuster's main project. That is another game, listed seperately by THQN, that entered development around October 2016.
Since the current GOAT Dying Light will drastically change with DL 2 and will drop zombies for the most part of it and the classic DI/DL gameplay gets lost, yes, I'm still looking forward or at least hope they go the classic way with it. Cause even if DL2 will be amazing and a good game, I will miss the classic approach.