Enough hashtags. Predictions!
In truth, they could show off a number of things. The Dojo was originally started around April so it's possible it could be something similar. I think they'll make the official website more official and add pages for stages, items, other content, and maybe even music. It will probably update more like Melee (every week or so). They'll show off one newcomer for sure. I expect it will open with a new trailer which will show off stages and what not. He'll likely expand on what the two games do and how they connect and probably the single player mode too. I expect more Wii U stages to be shown, like maybe a Starfox stage. He'll likely have some more footage and he'll state that the game will be playable at E3. I've seen some people say Pac-man and Mii will be shown, but I don't think it will happen. Sounds like putting the rumor before the reveal. I think Megaman and Sonic are the only two third party characters, which works as a lot of people like them. There isn't another third party character everyone can agree on and ones like Pac-Man has a strong negative response to them. I will say that if they are going to show another third party character. it would be either now of E3. For what new characters could be shown.......it could be anyone. Palutena, Ridley and Chrom seem likely. These three seem liked enough and well known enough that people will get behind them, but we'll have to see. There may not be any veterans, but I expect they'll show the veterans off slowly like the Dojo did. It wont be like the now where they are tied to releases and anniversaries. They'll say the release date if it's close.