I can't see the meta changing like it did from gen 3 to 4. Its the same game, but with more pieces and as you say, they seem to offering alot of back catalogue support.
My main concern is that tiering will be a nightmare with so many pokemon with one or two hyper stats but mediocre other stats.
Also, some of these new pokemon pose such new and strange stat-typing threats that old school offensive threats will probably beast early defences ^^
I really wanna play with all these hyperbole pokemon, that have 1 huge stat and the rest rubbish :P I wanna see how useful they can actually be in specific situations.
My appearance, ability, and awesomeness strike fear into the hearts of any sane battler and my thorny vines drop the opposing forces just an iron ball plowing into a man's genitals.