While we don't have a price or date for the 3DS XL Circle Pad Pro, Nintendo has posted an image of the add-on (the one on the left). It certainly looks like the Circle Pad Pro, albeit slightly less aesthetically unpleasing. And even though this shouldn't be taken as positive, at least with the XL, the system is already substantial in size, so adding even more to it doesn't seem quite so ... wrong.
Presumably, this accessory will be available in markets outside of Japan, though I don't believe we've heard such a confirmation from Nintendo yet. Either way, I don't see too many people giving the peripheral much thought until Monster Hunter season arrives.