If he said this then I think we only get 2 more stages sadly but maybe among them is Fountain of Dreams or Pirate Ship.
I still don't think Pirate Ship is possible based on the layout. The final layout should look uniform, and only Mario will cross over multiple lines (but with it split into main games and spinoff games). Fountain of Dreams would also be a great pick, the problem, again, is the layout. Kirby getting another stage, with one stage within the first two rows, would split Fire Emblem to multiple lines.
Here's the problem:
If there's no new stage in the first two rows, Skyloft appears next to Kongo Jungle 64 and looks very off.
If there's a second stage above the second-to-last row, Smashville gets shoved to the next line and looks very off. (I made a mistake prior; its actually Animal Crossing that gets split up.)
So, yeah. Either the stage selection screen will look very off when its finalized, or there is no new stage for any franchises in the third to sixth rows. Which includes Zelda, Kirby, and Pokemon, the most commonly brought up ones.
It would also look off for a standalone stage to be in the first two rows because all "single stage" franchises are at the bottom.
Either the stage roster is going to have a blank in the first two rows, or we get another DK/Mario stage. I don't see any other options.