I love the ideas I'm seeing but I also want to know what you guys think is actually going to happen. Even a rough estimate would suffice.
Probably raw number nerfs on Diddy
somewhere. He's simply too high-profile for Sakurai and co. to pass over, I think, regardless of what anyone else here thinks about the necessity of nerfing Diddy. The reason I specify raw numbers is that I'm not sure how devoted Sakurai is to his original vision of his characters. Tweaking damage and knockback is one thing but I'm not sure if anything more complex is really reasonable for us to expect. Sheik may or may not get a similar-but-lesser treatment, I'm not sure, and forget predicting anyone else. Sakurai's mind is kind of an enigma at the best of times. The rest of this is less "I predict..." and more "I would not be surprised if this happened."
Lucina may get the Shulk treatment where she enjoys a blanket 1-2% damage buff on her entire moveset. I think it's pretty well known by now that she's a strictly worse Marth since she's basically at his sourspot damage levels minus his special hitlag modifiers that made his sourspots safe on shield. If she did extra damage then at least she'd have a reason to exist on hit.
The main characters I want to see buffed are Samus and Zelda. Samus I think just needs some IASA frames on her missiles and let Super Missiles kill at maybe 150% or something. Tweak as needed for customs. (Power buff for Turbo Missiles would be a dream, I really like that particular custom even though it's kind of bootycheeks right now.) Zelda needs...something. Something drastic, I think. Fixing up her fsmash so that people don't fall out of it would be a good place to start, but beyond that I'm not sure. Din's Fire and Phantom Slash need to make me feel threatened when she pulls them out but right now...nah, nothing.
If I'm being honest, I doubt we'll see many "quality of life" fixes like removing helpless fall after Din's Fire, Burst Grenade, PK Flash, Giant Punch, etc. That's the sort of thing you just can't miss in basic QA which implies to me that it was a deliberate design choice for god knows what reason.