The thing is, I really want to say that Darkrai will finally stop being tier 1. But everyone said the same thing when HS was rotated, then again when BW was rotated, then again when the new rules happened. But every single time, it remained incredibly powerful. I think they'll all have to include regular Yveltal for sure, and I also think Yveltal EX will be the main focus of the deck (although my testing has shown that's probably going to be the case anyway), due to only needing 1 Dark and 1 DCE to attack as opposed to Darkrai's 3 Dark. I don't think it will be tier 1, but I think Yveltal/Darkrai will still exist until Darkrai is rotated. It might be in small numbers, but it will exist.