Through both the official Super Smash Bros. website and Miiverse, a new stage for the new Super Smash Bros. Wii U was announced with a screenshot. The latest stage is from a game that has had very mixed reactions, Metroid: Other M. The new stage is one of the most well known areas from the game, known as the Pyrosphere, where many big events occurred during the game.
The bigger tease from this announcement is from Masahiro Sakurai’s posting on the Miiverse of the screenshot where he said “Out of the blue, here’s a new stage–the Pyrosphere from Metroid: Other M! An enemy from Samus’s past may appear at any second…” This quote is obviously referring to Ridley, who appears in this area in Metroid: Other M.
The question now is whether Sakurai is hinting that we may see an announcement of Ridley as a playable character soon or if he just means that Ridley will be a stage hazard that appears at random times during the stage. Hopefully it will be the former, as the Metroid series definitely deserves another combatant, and Ridley is the most obvious option as he is Samus’ nemesis.
Based on the image being for Wii U, the assumption is that this stage will not be on the Nintendo 3DS version of the next Super Smash Bros. as the two versions appear to have different stages, the Wii U stages from console based games and the 3DS stages from handheld based games.