The 10th thing wasn't actually in that post, I was putting 2 and 2 together. There's supposed to be a conference on the 10th by Nintendo where they at least go over the release dates for Smash and Wii Fit in Japan. So that might also be the event where they show Smash to be playable, Reggie said there would be an event for the press to play it.
If it does happen, E For All having it playable wouldn't be TOO large a stretch. The game is released like a month and a half after that. It'd be great if it were there so we get impressions from real people who play the game and not the press that end with "The game looks to be shaping up and you'll be able to beat up Pikachu with Mario on December 3rd!"
Anyway, the source seems reliable enough. SRK isn't a nobody community, the guy is a Premium Member who probably has history there, and his story does hold up (and has pics).