In the latest issue of Famitsu, Nintendo has confirmed that a Circle Pad Pro for the upcoming 3DS XL / LL will be available later this year in Japan. As for potential XL purchasers who have shelled out the $25 for the original circle pad pro, sorry, but it looks like you’ve purchased a piece of ancient plastic.
Still, why is Nintendo even offering this when they should have built it into the XL system all together? Maybe it would be acknowledging their mistake, but who cares; why continue to annoy fans when the solution to a problem was in arms reach? At least the option is there. In any case, no price has been announced, nor are there any screenshots of the add-on available, but hopefully it won’t be as bulky as the original was and reasonable priced.