Would sprites for trophies REALLY be too much? I don't think they'd take up that much space, just the same amount as a character or two.

This is a quote from the FAQ, now you can say your 100% sure Shiver.

In that case we could drop trophies and have a roster 3 times the size of Crusade's

No, what I'm saying is a hundred or two trophies wouldn't be that much, not each trophy = one whole character

ok nvm

I speculate Assist trophies getting resprites/recolors so they can match their main character from their series.

I know this is most likely not going to be included as it features many ideas yet to be seen in the game, but that's what speculation is about, right?
How about we get a derivative of Fox's Smash Taunts?, only that this time, these are triggered by Kirby, Meta Knight, King Dedede (If we're lucky to get him) and any other future Kirby newcomer.
It can only be done in Halberd (which is yet to appear) and while the triggering is the same for all three, all characters have distinct ways of showing the trigger:
Meta Knight just grabs a cellphone from Amazing Mirror and contacts his soldiers (from Revenge of Meta Knight, which featured similar conversations a-la Star Fox, only that these were exclusive to the enemies).
Kirby looks around to the sky, as if Meta Knight's armies found him "spying" on the ship.
While Dedede, just does the same as Meta Knight... unoriginal I know.
All 3 variants feature different characters in the conversations. Kirby's features only the Meta-Knights (including Meta Knight), Meta Knight's features the Meta-Knights plus Sword and Blade Knight, and Dedede's features the Meta-Knights, Bandana Dee and himself.
One example of Kirby's:

Axe Knight: Ack! K-Kirby's here!
Sailor Dee: Oh gosh! What are we gonna do?
Mace Knight: He mustn't interfere with our plans!
Captain Vul: Darn! We were so close!
Axe Knight: Wait, who's that?
Mace Knight: Someone we don't know about, for sure.
Axe Knight: Wait a minute, it's fighting against Kirby!
Captain Vul: YES! It's on our side! We'll wait until Kirby's been beaten to attack.
Sailor Dee: Let's just hope it doesn't try to attack us after that...

One example of Meta Knight's:

Captain Vul: All soldiers prepare for attack! Prepare the Main Cannon #2 to blast the intruders! We must inmediatly terminate the intruders in the ship!
Axe Knight: For what? One, two opponents? I'm sure Sir Meta Knight can take care of this.
Captain Vul: Whaaat!? How dare you!?
Meta Knight: Hmm... I believe he's right. Let's not waste energy for nothing.
Mace Knight: You know, I always wondered if Meta Knight is actually on our side. I don't know, I have the feeling he'll destroy this ship someday.
Axe Knight: Yeah, that would be a real Knightmare!
Captain Vul: Ha ha. I'm sure if Meta Knight had to choose between destroying his own ship to grant his biggest wish or keep his ship alive, he'd chooose the latter, right?
Sailor Dee: I think we got a game for that...

And one example of Dedede's:

Axe Knight: Wait, who's that?
Bandana Dee: It's the great King Dedede of course! Bow before him!
Mace Knight: Well, how can we help you, King Dedede?
Captain Vul: I bet he needs a monster to clobber that there Kirby!
Mace Knight: That's what we do best at NME!
Axe Knight: It better come with a moneyback guarantee!
Sailor Dee: *plays Sax solo*
Dedede: ...

Like I said, I'd love this kind of easter egg in the game, but I'm fairly sure it won't happen. Hahaha Hmph...

Secret Conversations sound so awesome!

i speculate adventure mode

^Yeah. Especially Renji. The comparison between him and Ichigo is quite funny actually.

I speculate that Jungle Hijinx will get some sort of new unique spice to it (doesn't seem to be very popular lately), that palette swaps will be a little bit "better" (as in specific areas shaded - I've heard it's quite hard/impossible but even a tiny amount of improvement would do) and that characters, stage hazards, background characters and pretty much the entirety of the game will be completely originally sprited by the end of the full game.

Also I speculate some of the cut stages from previous demos (Mushroom Kingdom II, Castle Wily, Temple of Time, the old Waiting Room and the old Yoshi's Story which was called Yoshi's Island in the original SSB in particular) to come back and be labelled under a new stage section called "Demo Stages" and that they'll have a little bit of rework done to them. Very impossible, I know, but I kinda miss Birdo firing those eggs.

Aaaand I speculate that White Mage will be a rare AT, completely healing her summoner instantly when released.

It is impossible without dramatically inflating the file size, unfortunately.

With 3D models and textures, only one image is needed for every animation because it's the model that does all the legwork.

With 2D sprites, costumes would have to be edited frame-by-frame and loaded independently. This means that several copies of the same character's spritesheet would have to be saved, no matter how simple a given recolor is.
They've worked around this by using Flash's built-in blanket filters, but those aren't very advanced at all; those just basically put a piece of transparent plastic over the existing image. The entire image. There's no option to only recolor certain areas.

A few times I've had the idea that they could just have the character sprites split into two parts: those that should be recoloured, and those that shouldn't, so that way the colours can be changed without changing people's skin. With both objects as the character as a whole, and only one filtered, it'd look decent. I don't believe this would affect performance or filesize too much.

It'd still be a lot of work though, since they'd have to edit every single sprite they currently have in game, and possibly even some minor changes to the system that does the recolouring, so that it is specifically filtering the right part, rather than the whole sprite.
I feel like this is the simplest option that would work decently, even if it does still leave the issue of characters like Sora and Ichigo barely changing.

Of course the more complicated option is to split up every differently coloured section, and use a separate filter on all of them. This way each part could have a base of full red like Mr. Game and Watch, and then proper colour swaps could be done using just filters, without duplicating the sprites. I doubt this would have much of an effect on filesize either, but with all of the different objects that would be filtered, I imagine it'd be pretty bad for performance.

This would of course be the best looking option, because every character could have any possible recolour they wanted, without making it look super strange, but it'd take even more work than the other one, and I don't know how much lag it would cause.

I do hope that the devs eventually decide on something to improve the colour swaps, whatever it may be.

If someone hasn't already said this: Maybe a tournament mode. Of course it would take FOREVER to do (and might be impossible) but, if it is possible, then I say it's likely.

I'll split this into two parts, one likely and one dream
The likely part-
I think it would be much like he main game SSB games, with a few cool features.
-Double Elimination option
-Seeding
-Maybe a "World Cup" mode with a group stage
-Best of 3/5/7

The dream-
An online version of it. This could be REALLY useful, seeing how much the community has grown. The way we do t now is great, but this could really be something game-changing
Some features:
-Everything offline has
-Password system
-Max/Min participants
-Check-ins
-Invites
-League-type things (like Swiss tourneys, but longer)

And for a mini speculation, I speculate a new McLeodgaming stage. It's not likely, but I could see it happening

Tell me what you think of this! *prepares shield*

*Hits you with a fully charged shieldbreaker* just to tell you I like the idea.