Yeah, they're probably not going to use sprites for much of anything in XY, with the exception of things like the HUD and other displays that commonly use sprites. No sprites for the Pokemon, though; it's a billion times easier to just re-use the 3D models, since they scale nicely.
Anyway, Serebii does indeed has a plans. He's already able to get pictures of the models from Rumble Blast. Example: http://www.serebii.net/rumble2/pokemon5.shtml
THAT'S MISS HOME ROWED TO YOU eyes glazed like a mirror to heaven