If they became popular then pokemon ranger would just become more of a 2 of.
All out offense is generally the best way to win which is why usually high damage output decks win the big tournaments. Rayquazza is a pretty great option but without Karen, coming back from a stadium switch or even worse parallel city can really hurt the strategy unless they withhold a couple basics in hand as well as super rod right after. Mega Sceptile can be great if you can loop heals but it lacks good offensive pressure without ariados and is walled hard by glaceon and Regice which ironically makes water toolbox(replacing Toad with something currently wanting to use Primal Kyogre or MGyrados) a good deck to beat Sceptile. Volcanion seems to be getting some hype but i think focusing to much on flareon is not a good idea due to the fact that it hitting hard numbers could take a while and there is always a swift lysandre knock out to ruin all your hard work(My friend actually has a great list i think will be pretty good but i wont divulge any information). Greninja is great but losses Muscle band at the same time that it really needs it as hitting 220 is now very important and also with everyone and their mother trying to put garbodor with everything else it could make it difficult to win as a very specific tech is needed to win against a garbodor deck but its still a nuisance. Raichu is not as good for the same reason that rayquaza is going to have issues except raichu's is maximized by the fact that it has less room for recovery due to evolution lines and also looses Muscle band and Crobat. Mega Mewtwo X is less viable without bats, landorus, Battle compressor, and Dimension valley which is a shame because its technically better than Y. However Mega Mewtwo Y might get a foothold in the meta as it has allot of advantages namely power and the fact that it can be used with any type of energy. I personnaly like the idea of using Mewtwo Y with Clawitzer but as i learned with Mega gallade having 2 evolution lines can be clunky but its still a possibility. another benefit of using clawitzer is that you can use Rainbow energy as your Special energy to accelerate(Alongside DCE of course) and that opens up other strategy's to employ. Magnezone/Raikou/Kingdra is a deck that is mostly rogue but not inherently bad and can definitely win if you let it. Turbo Giratina(Reshiram) is a great deck that loses nothing and has recently gained Special Charge which will shore up his old weakness but pokemon ranger can hurt a bit however its a solid counter to Rayquazza as they cant Hex and Ranger on the same team. Zoroark/Yveltals is another deck that will likely be great for next format but i dont need to explain that. Lastly i'd like to express my joy at the temporary death of item lock. Without AZ Vileplume is no longer nearly as good as it was and with the loss of its favorite partner vespiquen(No Battle compressor) we can hope to have much more fun games now that the more toxic decks have left the format.