I know that there was talk about remaking Ruby/Sapphire, and that possibly BW2 would tie into it.
Herein lies my theory;
There are some big things going on in the pokemon world. Pokemon Conquest releases next month and your starter is Eevee, there is a Darkrai event going on, a bitching anime trailer for Black and White 2 came out which oddly, had a Lucario starring as the main character's pokemon?
In the past, the Pokemon center has released plushies corresponding with events, and usually corresponding with the current generation. Zorua and Zoroark came out around the movie time, the three dogs and Celebi around the time those events were going on.
recently, new Pokemon plushies were added to the pokemon center. Darkrai, Eevee, Umbreon, Lucario, Kyogre, Groudon, and Raikou
Darkrai ties into the event. Eevee and Umbreon to Pokemon Conquest. Lucario to BW2. So what, pray tell, brings us Kyogre and Groudon out of the blue? Why now? could it be a tie-in to third gen?
I must admit though, I have no theory for Raikou....