I meant big changes in the context of a reboot. Yes, big changes will keep happening, but they will be additive, not substitutionary. I don't disagree Sakurai will keep looking to innovate, but at the end of the day business trumps all.
Unless my memory is lapsed, Nintendo has never done a full blown reboot following a largely successful title. On the the contrary, they become less inclined to innovate.
But, it is true there will be a tipping ppint when it comes to newcomers. Will it be at 80? 90? 100? But it certainly is more of a long term issue.
Tipping point has basically already been passed. The roster in 4 is already starting feel very samey in terms of playstyles. 70 is basically the max most fighting games go for, with the largest roster ever belonging to I think Capcom vs. SNK 2 (or was it one of the KoF games?), which was a team-fighter and it had a roster of sub 80.
No, DBZ Tenkaichi 3 with its 150+ character roster does not count, and if you'd played it, you'd know why. There are basically like 10 character movesets distributed among the roster. Everyone plays the same.
Thus, point being, the budget and dev time for games is NOT infinite. With each new installment, as the roster grows, so does the dev time grow exponentially. No, it's not as simple as just porting stuff over. If you're working with a new engine, you've gotta redo everything. Plus, the playtesting and balance. That's what takes up 80% of development time in a fighting game. For every change you make to the game physics to the game, or every new mechanic you add, every character has to be playtested against every other character on the roster again and again for bugs, exploits, and balance issues.
Finally, reboots are common among fighting games. Just about every major franchise out there has been rebooted at least once, and its got nothing to do with sales. More often than not, it's simply the devs wanting to try new things with the mechanics or roster. Something Nintendo is already very familiar to begin with.
Personally, I'm not holding my breath for it, but there do seem to be a few hints this game might be a reboot.
-right handed BotW Link
-Retro logo
-Short dev time
-bloated roster
-popular characters not returning, making a continuation of 4 seeming inferior by comparison
-franchise is starting to get stale and less exciting for many
-eSports focus on Nintendo's part
etc...
We'll see.
That said, the franchise will have to be rebooted sooner or later.