I didn't want to read too many people's predictions, so if I throw doubles in there, I am trying to go off the top of my head.
1) There will be at least 101 event matches.
2) Break the targets will become a multi-player mode, where they constantly appear and everyone tries to nail the most while attacking your opponents to keep them away.
3) Online mode will end up having a ranking system, as they change their mind last minute (If Strikers Charged has it, it's within reason)
4) A final fantasy character is playable in the game
5) Other "Punch Out!" boxers will make their way in as ATs
6) The Sub Space Emissary main mode will provide an insane unlockable - but you have to beat the mode with every set of characters, controlling both members at least once.
7) Two unlockables in the game will be game trailers of long awaited series revivals - Kid Icarus and Earthbound.
8) More than 10 classic stages will be available from the first two games, bringing the total stage count in the game to over 35.
9) There will be a gravity-less mode where there will be moving platforms on the four sides of the screen that are there to bounce off of. The control of your character will be rough, as you will have to keep yourself in the area by attacking your opponents, using projectiles to change your trajetory and all sorts of crazy stuff. (And this will be the only mode allowed in tournaments - just kidding
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)
10) The final character that is unlockable will be Goldeneye's James Bond, giving the game 36 characters total, and unlocking him automatically unlocks the final stage as well - Facility.