It might be too early to tell at this point, but I think that Tapu Koko-GX is probably going to be tier 2. It hits M Ray for weakness and its GX attack is one of the best in the new set.
What do you think will happen to Mega Ray with Sudowoodo in the meta and lightning making a comeback?
Not only Lightning and Sudowoodo. Trashalanche Garbodor is death to that deck. While M Mewtwo was always good against M Ray, adding in Trashalanche makes that match up downright bad for M Ray in the games I have played. Granted, I am also rocking Wobbuffet in my M Mewtwo list, but that Garbodor brings M Mewtwo to a whole different level.
I think there are going to be a lot of decks like this coming out of this set. Honestly, I think Pokemon did a pretty great job of adding another set that shakes up the meta right after adding a set that shook up the meta. If SUM3 is anything like the first two, we can keep looking forward to new meta decks.
Regarding the meta list.
Quad Sylveon is going to be T1...T2 at the very worst. That deck is a very hard out.
Also curious to see where Quad Wobbuffet gets placed too. It seems like a T2 deck simply because I am not sure how well it will do against decks that don't fit the current meta's template (Quad Lapras and Quad Sylveon) are going to be hard for that deck to beat.