I don't really know how the online is thought to turn out, but it'd be cool being able to set up a tournament lobby with rules customizable by the host. Like;
4, 8, 16, 32 players(or maybe even onwards),
how many stocks/match,
time,
single victory or best of 3 maybe,
damn, even items for more casual tourneys,
picking what stages can be picked,
or being able to set it to random a selection of stages,
setting a single stage for the tourney,
maybe even character banning, though I personally probably wouldn't use that feature (lol)

People could join in, take up spots, and pick their characters in the room. Imagine it'd look a bit like Brawl's tourney lobby, visually.
When everyone press their ready button, the host can start the tourney and the matches start. Or maybe there could be room options setting it to 1 match at a time, for those who like to spectate their opponents matches.

Whew, got a bit carried away there, and maybe it's just me, but I think that would be an awesome feature.

Yay, speculating, yay!

-1 more Sonic stage, from one of the dreamcast or next gen games
-Sasuke, if not a character, becomes an assist trophy

^
Yeah...

No discussion about characters incidentally. Said in the first post. Just sayin'

There should be an option to import music into the game. I think it would be cool because then we could have whatever we wanted playing in the back round. Yes you could just have it playing in the back round, but it would be cooler if it was sinked with the game.

I agree, that actually sounds like a pretty cool idea! Anyways, I can't believe that I forgot to add these to my speculations today seeing as how these are two big things that I'm gunning for to happen. I speculate a new sprite or a flash animated Mario Finale and that Mega Man will get a new final smash. I mean honestly, you all know that Super Adapter is a bit boring, slow and I mean it can only do one attack. What about a more unique final smash? Oh yeah, and hopefully, Jigglypuff's Puff Up and Samus's Zero Laser will both act much faster.

Let's just hope the devs are listening.

Also going to speculate a bigger Hueco Mundo and MKIII. Maybe hazards for MKIII too.

Still pushing for stamina mode.

Yeah, but some chars like Kirby have only 1 taunt. :/

Adventure, Classic and All-Star Modes

An opposite mode for Invisible Mode seems legit considering it's the only mode without one.

I think Sonic should get a new final smash. Maybe Excalibur Sonic.

I'd rather not see that form ever again.

I agree.

My vote.

The only thing that game had that was decent was music (Which can be said about pretty much any Sonic game, really.)