Normally I'm not one to get into these types of topics, but I find it ammusing that ever time a 3rd version(Or sequels in Gen V's case) come out people expect new pokemon mid-gen. Hell, this happened even with yellow. And the 2 sets of remakes. I remember people thinking FR/LG would add munchlax to the Pokemon available. When B2/W2 came out, some people who saw the studiomons' sprites without context thought we were getting new pokemon, though in that case it was slightly more reasonable because all of a sudden these strange battle sprites that didn't look like the 649 known pokemon floating around the net.
They never add new Pokemon in the past, just new/alternate forms.
They will never make sequels; every pair will have a third version They will never make dual-type moves, that's too complicated They will never make a new type, the chart is fine as it is They will never make a legendary who breeds, that's just impossible They will never make a gen without a legendary trio, it's tradition They will never make a god Pokemon, that's just fandom nonsense They will never make a movie about a non-legendary, that's ridiculous
Face it, Game Freak does new things and breaks the formula all the time. What basis do we have for saying that there can't be new Pokemon mid-generation?
"The difference between fiction and reality is that fiction has to make sense." -Tom Clancy