The Nintendo 3DS version of Super Smash Bros. will have a stage based around Lumiose City from Pokémon X and Y.
Game director Masahiro Sakurai teased the stage with an image posted to Miiverse. Alongside the image was the caption "The Prism Tower rises above Lumiose City. Up until a few seconds ago, the fighters were brawling on top of that tower. No, really."
Sakurai didn't specify if the level was going to be in the Wii U version as well, but the picture posted specifically mentions the 3DS.
Unfortunately, we're still awaiting the release date for the new Super Smash. The game was first announced for Wii U and 3DS back at E3 2011, so I'd say it's probably coming soon (maybe this E3?).
