Given all the setup for Big Mom and Elbaf, she's probably going to show up there. Fighting Kaidou being bigger than marineford doesn't have to involve two emporers, give how Kaidou has been described and all the forces we know are already involved just on the good guy's side.
Also, Take Oda's 80% estimate with a grain of salt. Given his track record of estimating his pace (extremely bad. Mid skypeia he said Merry would die "next year" for instance.), the number of things and places we know still need to be adressed (a lot) and the overall pace Oda tends to make any given arc nowadays (longer than it used to be) we're probably not as close to the end as he thinks. And of course, his 80% can mean locationwise, storywise, volume wise, or years spent, and those all have different meanings.
Obviously Oda knows his plans better than we do and it might turn out that Elbaf is just a quick 10 chapter mini-arc, and Raftel might be a super short setup island rather than a big payoff, and he might take a few narrative shortcuts to trim down some things he would have spent more time on in the past, (like cutting down all the unique zombie generals on Thriller Bark in one go) but if he keeps to anything resembling the pace he's been taking for basically everything and his tendancy to try and wrap up big arcs around the 100 chapter mark…
Kaidou-2 years (minimum, given the ammount of players involved)
Elbaf- 1 year
random stuff (new islands, vegapunk arc, reverie part 2, etc.) 1 year
Raftel- 1 year
Final war- 3 years (strawhats fighting blackbeards 1 on 1 with each SH getting ONLY 2 chapters apiece and Luffy getting more would still be 50 chapters by itself) plus epilogue
Note I'm equating 1 year to about 50 chapters, though Oda doesn't quite hit that pace anymore. And that's lowballing the length of Wano and the final war.
The very, very fastest I can see the series being done at this point is about 7 years (about 120 volumes for the 30th anniversary) if Oda really guns it, but after WC went as long as it did, and didn't resolve a bunch of its threads, I have a hard time seeing it be much less than 9 or 10 years at this point.
And lets be honest, if he gets to year 33 and is close to wrapping things up, there will be editorial pressure to slow down and make it last until the 35th anniversary for marketing... as Naruto was clearly made to do.