In gen IV we had the shiny beasts and nasty plot celebi that unlocked stuff in BW, namely the only ways to get Zorua or Zoroark at that time. There was also the unreleased lock capsule which would have gotten you tm95, snarl. So do you hope/think they do this again for XY with events already or yet to be released, or do you wish they abstain from it at all costs? Would another exclusive pokemon be allright again or would you wish they unlock something different this time around?
Personally I thought it was pretty awesome that the seemingly normal events unlocked something in hindsight, and I'd be pleasantly surprised if the same thing happened for for instance the Meloetta or Mewtwo events. Maybe this time unlock an exclusive area or something rather than just pokémon.