Super Smash Bros. will not support the Circle Pad Pro accessory for 3DS, according to a support page on Nintendo of Japan's website, as translated by NeoGAF. With the recent announcement of a new 3DS and 3DS XL, the upcoming entry in the Super Smash Bros. series will reportedly favor the new devices' use of extra shoulder buttons and C-stick as opposed to the accessory that added a second circle pad and shoulder buttons to existing 3DS systems.
This implies that players using a traditional 3DS or 3DS XL will be locked to using controls specific to those consoles without the extra buttons and joystick. The game will launch prior to the new hardware; Super Smash Bros. for 3DS is due out September 13 in Japan and October 3 in North America. The revised systems, which will be region-locked, will launch October 11 in Japan and won't make the calendar year in the west. The other version of the game for Wii U will arrive this holiday season. We've reached out to Nintendo to confirm the 3DS version's lack of support for the Circle Pad Pro and will update as we learn more.