No coincidence. Nintendo always releases new systems on the same day as a big game release.

Pokemon X and Y are a very big release and should be big with the younger demographics, the same group who Nintendo has repeatedly said shouldn't be exposed to the 3DS's 3D, so this makes sense. With the apparent lack of the clamshell design, it seems like the 2DS is just a low-end 3DS for that younger crowd, much like what the GBA Micro was to the GBA.

I do wonder if this has anything to do with the reports I've heard that have said that the X/Y demos don't have 3D in the overworld...