@GetsugaZoro:
They said when they revealed the game that this is an alternate storyline, it's not a sequel, or a prequel, its an alternate world.
The phrasing "alternate storyline" has been used in some capacity in the box description for nearly every 3rd version since Emerald.
There is a slim chance that it could be a sequel like B2W2. The fact that we have little information doesn't rule that our per se.
Especially given what we've learned over the past few games, and especially the post-game of SM. We know that there absolutely is alternate universes/timelines and one of these includes the non-Mega Evolution timeline of Pokemon Emerald and the one the current games have shown. This could be a 3rd version with a postgame that acts as a sequel, perhaps interact with SM. It's still just too early to predict what they mean this time by "alternate story".