i bet the end of the season of the lost we will fight savathun's worm. as for the witch queen raid, i don't think we will be fighting the anomaly, because that is the overarching villan that certainly has to wait till the end. savathun wont be the boss either, ad the devs had said. it could possibly be fikrul, using a recurring character just like taniks. it could also be xivu arath, to tie up the third sister narrative. i personally think it will be xivu arath, because its known that she is being controlled by the dark, and has domain over both scorn and taken, given by the dark. perhaps the raid is xivu arath attempting to get even more power from the pyramid, and we have to stop her? or something is emerging from the pyramid into savathun's throne world, and we are trying to stop it? i think savathun is going to become a character akin to mara sov, and less like oryx. i dont think we are going to end up killing her.
I also have a feeling that we won’t be killing Sav, they’ve built her up too much to kill her off. She may have more integral story threads to follow but ultimately I feel she will betray us in the end (in Lightfall maybe)