For no particular reason, here's a handful of predictions on how I think certain characters will change tier-wise in the future:
Realistically, this guy doesn't have anywhere to go but down. Strong grab game and kill confirms aside, he simply has too much working against him. Being ultra easy to combo is well-known, and wouldn't necessarily be so awful in itself. However, he's also definitely one of the easier characters in the game to edgeguard - the weakest of meteor smashes can prove fatal, and even if he doesn't die off-stage, he'll be taking a good chunk of damage at a minimum. Critically, he also struggles against disjoints a lot, and struggles to put his good range to much use because of it. I can see him being as much as 10-15 positions lower given some time.
I don't think the full implications of a 'time out' Sonic have been fully realised yet. Played sufficiently defensive, it honestly wouldn't surprise me if he eventually becomes top 3, even.
Rosalina, by contrast, I reckon will settle into #6-10 at some point. Don't get me wrong, she'll always be terrifying to fight against, and can wreak havoc once momentum is on her side... but there are a number of MUs where things can go seriously wrong when momentum
isn't on her side, and I reckon that will prove detrimental enough to keep her out of top 5 (she'll always be top 10 miminum though)
Sooner or later folks will realise that there really isn't enough justification for having her more than 5 or so places below Marth. Look at it this way - if Marth wasn't in this game, and Lucina was a standalone character, would she still be ranked where she is now? Somehow, I highly doubt it...
May
eventually overtake Ganon and/or Mii Swordfighter. Maybe. (N.B. This one is more wishful thinking than anything else - honestly, Jigglypuff's biggest problem is that Smash 4's game mechanics almost seem custom-designed
specifically to screw Jigglypuff over)