That's in the Japanese version of the trailer. In the English version, its already on the second page. It shows the updated lineup--Green Greens (or Dream Land 64? can't remember which) and Suzaku Castle are in the top row of two, Miiverse, Hyrule Castle, and Peach's Castle are in the middle row of three, and lastly the third row has room for two stages, with Super Mario Maker on the left and a blank spot on the right.
Its not entirely too new in a sense, but TF was made by Retro, located in the US, as opposed to Super Mario Maker and Yoshi's Woolly World which were made in Japan.
EDIT:
https://www.reddit.com/r/smashbros/comments/3l0exp/evidence_of_another_stage_coming_explanation_in/
This was posted in the official DLC Character Discussion Thread, but I'm reposting here.
Super Mario Maker is marked as stage_5.jpg. stage_4.jpg does not exist, while stage_1 is Dream Land 64, stage_2 is Hyrule Castle 64, and stage_3 is Peach's Castle 64.
Suzaku Castle is not marked as a solo stage. There's currently one stage missing, and its a standalone stage, so it won't be bundled with a character. Either its another returning stage, or its a new stage for a franchise already in game right now.
This also means that whatever character potentially gets added, its very likely NOT a character from a new franchise. It could still be K. Rool, they just won't bundle the stage with him. Which makes sense, because any stage he could potentially work on could also be used for any other character, so people may not want to be forced to buy him and the stage at the same time. (If its a stage associated with Rool, though, there may be a bundled option.)
Of course, it could just as easily be Kongo Jungle Melee.