Thunderbird77 said: It hasn't, It was always pretty clear when we got a new gen. Brand new pokemon and brand new region. |
As I pointed out literally two posts before you, ORAS got a heap of new mega evolutions, which are practically new pokemon. It got multiple new gameplay innovations. Which means there's not a whole lot of difference between the move from HGSS to BW and the move from XY to ORAS. The only real difference is ability to transfer pokemon from ORAS to XY... but you could do that from Gen 2 to Gen 1, too.
Hence why I described it as "blurrier", not "completely absent". Suppose this next pair were set in Kalos, but had brand new pokemon. Would that be a new generation, or not? What if it was in a brand new region, but the only "new pokemon" were mega evolutions plus a single mythical pokemon (magearna)? What if, like Gen 2, it has new pokemon and a new region, but you can travel to Kalos and can transfer pokemon that were available in XY back to XY?
Any and all of those are plausible, and wouldn't be much of a stretch from what has happened within generations so far.