Someone on Brawl Central forums mentioned this, and I thought I would share it. just to have some sort of hope, even if its delusional. Take it with a grain of salt.
In the intro video that has been leaked, we see Sonic and Snake. No other third parties to be seen. Of course they would not blatantly just put the other third party character(s), IF there are any. In the credits, below the start screen, we see all the companies involved as of the video. There are several theories for this:
1) Konami and Sega are the only two third party companies involved with the game at all. So, in theory, IF (I stress if) there is another third party character, it will be either another Konami or Sega character. This does not mean it will be Knuckles, but if this is the case, then this, along with the Famitsu recognizing wall cling and gliding, could possibly highten the chances of Knuckles.
2) They only show the companies with characters represented in just the opening video. This would also give hope to supporters of Megaman, Sora, Geno, etc.
3) In order to keep any other companies secret, they didn't include the character, and can add them in as they are unlocked. I personally think this is unlikely, especially if the said company involved wants credit, wouldn't they be on the opening credits anyways? However, this may be a thought to consider as well.
I, of course, subscribe to number 1. The last two just don't make a lot of sense to me, but I also would love to see Geno in this game, so anything could work. I also believe that there are no other third party characters, but that is just my opinion. Sadly, if that is the case, then it gives more credibility to the "Nightmare 35" roster.
Everybody keep their fingers crossed, form a circle, build a fire, sing "Kumbyaa", and grab your shovel claws, just in case..........
We're pulling for you, Knuckles!