Just want to throw my two cents into the Shovel Knight thing
Why it wont happen
So far, the game hasn't been released in Japan yet, so its very likely Sakurai doesn't even know who Shovel Knight is. Keep in mind this is the same guy who didn't add Takumaru, a Nintendo character who was born alongside Pit, Link and Samus, because we wasn't well known outside of Japan. Shovel Knight, according to Yacht Club Games, has only sold 700,000 copies across most major platform. That's good for an indie game, but compare that to any Nintendo or the games from the third party series in Smash, that's pretty poor. About 60 percent of the 3DS's sales came from Japan, so it makes no sense to add a character who Japanese players don't even know. @
PushDustIn wrote a good article on the issues of Shovel Knight
Why Shovel Knight shouldn't be in
Adding Shovel Knight would be Smash jumping the shark. The reason the third party characters work is because Sakurai is discriminatory. So far, all the third party characters have been huge names with multiple million sellers. Moreover, all of these guys have been around for over 15 years. Shovel Knight is only about a year old. The other third party characters have proven over the years that they are well loved and iconic. The same can not be said about Shovel Knight. I know many fans will clamor because "Shovel Knight is amazing game," and very successful, but that doesn't mean it will be in 5-6 years. Look at Angry Birds. The game was very popular a few years age,
but now the developer is laying off employees. Nothing gold can stay.
Adding Shovel Knight is a slap in the face to everything the series has built up. It not only hurts the allure and luster of third party characters, but the idea of a Nintendo fighting game in general. So far, the only new character added as DLC was a third party character. Smash 4 already added 3 third party characters despite adding few characters than the previous game. It no longer becomes a celebration of Nintendo lore but a big marketing gimmick. It will kill the magic of Smash.
What will really happen
The PAX announcement wont deal with Smash at all. Shovel Knight has special content on the Playstation and XBox, but not the Wii U. I expect the announcement will be about special content on the Wii U version and it will likely involve amiibos. You'll be able to scan in an amiibo and it will introduce a Nintendo character in some way. Shovel Knight will also have an amiibo.