>>50618541I think it's pretty clear these are pokemon past and future in the same way that XY were supposed to be pokemon life and death, or BW are pokemon yin and yang.
They don't actually call them that because the games names as an individual game wouldn't work or other such marketing reasons. But that's what they are.
That being said, the starters never play into the legendary/game theming so that won't be relevant here.
