It's worth considering the type of game that could support a 90 minute roundtable discussion. For example, Nintendo's roundtable in 2011 covered Skyward Sword, 3D Land and some other single player games in the same window. Could you talk for 90 minutes about Metroid without just showing a huge part of the game?
Pokemon got one all to itself last year (iirc) because they went over the new mechanics, the engine etc. Smash gets one this year, because they'll be able to talk about the fighting mechanics, the connectivity and the new characters.
Nintendo usually have a general roundtable to cover their first-party games, so something like Metroid or Mario could easily be part of this roundtable while the "exclusive" roundtable is for something else. They usually don't announce their normal roundtable publicly either, so it's hard to know if they're planning to host that or not this year, but it's worth considering when predicting games.
Or it could all be nonsense, and it's just 90 minutes of them saying "We're sorry for Other M" as they reveal a sequel to Fusion.