I wouldn't say this warranted a thread, but whatever, I can dig it.
Well logically, it would be kind of asinine if he didn't say anything. However, if he does say something, it may range from some of the following
- Sakurai mentions it on twitter; adds in a little juicy piece of info or a hint of something
- Miiverse picture with a mode from the previous games; i.e. Master Hand present on FD, target test picture with info about their complexity (character specific or leveled ones), Board the platforms etc.
- Miiverse picture with some of the original 12
- Miiverse picture with a returning retro stage
- Miiverse with a new character; unless its a very known veteran, seems unlikely to me because it doesn't correlate with the anniversary
- Direct scheduled Tuesday, revealed Monday, within we could have
- A trailer
- Character reveal (s)
- Release date
- All of above
If it's not something related to these i'd be surprised. Tried to be as analytic as possible.