I think rain might be supreme just because it hits fire, ground, and rock for SE, almost all of them carry ice beam for grasses, and hits ice and steel for a STAB rain boosted neutral. SS isn't going anywhere because it will take a lot to shift T-tar from OU, and it won't be bad there, just maybe not as good as rain. Cloud Nine cannot reliably counter imo, but I am not suggesting weather is uncounterable. I think Politoad will become OU for usage alone, but Ninetails might have a solid home in UU. Of course, if there zre good sun cores, who knows, maybe Ninetails will be OU. I think weather will be more viable this gen then any other for sure. But a lot of winning with a weather team has to do with teambulding skills and prediction, and I can see well built Sun/SS teams destroying noobs with rain teams.