I took a look at the
uncollected chapters in the series to try and see when this fight could end, as well as when the series itself may end. Chapters in this series have consistently been 19 pages so Volumes have consistently collected 9 chapters. Volume 19, released last week in Japan, ended on Chapter 169. Here's what the next few volumes should look like:
Volume 20
-Chapter 170 (Kokushibo fight still going, all participants are in) to Chapter 178 (Kokushibo flashback ends, he fades away)
(Fun Fact: The anime S1 wasn't even done yet when the early chapters of this volume were released)
Volume 21
-Chapter 179 (Tokito dies, Genya fades away) to Chapter 187 (Yoriichi flashback ends)
Volume 22
-Chapter 188 is where this one starts, theoretically ends on 196 which is 3 chapters from now (193 released last week)
So the fight may end on 196 or a bit before. If it does, then Volume 22 may be the last of the series but I doubt that would happen and I think even if the fight ends in the Vol.22 chapters, there'd still be at least one more volume. Otherwise it'd feel like we're rushing things.
It's also possible that the fight and the series would end in Vol.22 but it'd have a slightly higher collected chapter count to allow for an epilogue. Or the fight could go past even Vol.22 and into Vol.23.
I guess how long the series has left depends if Muzan gets a flashback, how long that takes and then how much we get after that to wrap things up. If Volume 23 were the end of the series and it collected the standard 9 chapters, then the series would end on Chapter 205, which is a neat number. But I wouldn't be surprised if we go past that, especially if this fight is still going on past Ch.196/Vol.22.
Personally, while I'd like for this fight to end asap, I'm not in a rush for the series itself to end and would like to see a Muzan flashback as well as a nice aftermath.
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Random but
bunkitz remember in the MHA thread when Viz finally started releasing Demon Slayer volumes and we were like "Demon Slayer? That's a boring name"? Household name now lol.