I think is kinda futile thinking about WSJ's future, kinda like how Nintendoomers always said Nintendo was gonna fail..
Think about it, Jump got super popular during the 80s thanks to series like Ring Ni Kakero, Arale, Captain Tsubasa and Kinnikuman..
Those eventually ended and sure other Jump anime never got to the
heights of Arale (it had like a 36% at its peak rating back when it was aired, and as said by other users made the manga sales Jump from 3 million to like 15 million with only 6 volumes!)
Other main stays of the magazine continued like Kochikame and Jojo would start serialization later, along the way mangas we consider classic today like Hokuto No Ken, Dragon Ball, Captain Tsubasa, Saint Seiya began and ended their serialization, these are manga that shaped generations, not only in Japan but outside it. Think about it,
when Dragon Ball ended no one would have thought there would be a manga that would surpass it.. While maybe not internationally or in widespread success outside Japan, we now know the undisputed king (Talking sales here, don't want to start any arguments) is One Piece, but back when DB ended.. People probably didn't think anything could even be close to it in sales/popularity, and yet One Piece started serialization just one year after Dragon Ball ended.
Back in the 90s YYH, Slam Dunk and DB all super successful hits finished within 2 years apart of each other, and sure magazine sale dropped but then Jump got One Piece, BLEACH and Naruto within 5 years of those series ending (Along with a lot of very powerful properties that still run to this day like Yu-Gi-Oh! and Prince of Tennis, AND with other great and best-selling series running like Shaman King, and of course Hunter x Hunter which)
The 2000s brought us other big series like Gintama, Reborn, Death Note, Haikyuu, Assasination Classroom, Kuroko no Basket along with other best selling manga, I'm just skiming through 20 years of manga in WSJ, but those are the ones out of the top of my head...
Beelzebub, Nisekoi, Toriko, Assasination Classroom, Naruto, BLEACH, Kochikame, Kuroko No Basket all ended between 2014 and 2016, two years apart from each other. That's 8 manga and not just any manga, it's pretty much the biggest series Jump had in 2014 half of its (most successful) line up gone in the span of two years.
Jump sure seemed in a crisis back in 2014 with both BLEACH and Naruto reaching their endings (At least me and lots of other users assumed so).. And now we have
Kimetsu No Yaiba that's literally breaking every record possible, a feat that just a year ago no one suspected would happen and certainly not by Kimetsu No Yaiba.
The beauty of this is that every series that has shaped Jump, a "pillar" of Jump if you will, has reached new heights in different "ways". It's kind of like a baton pass in some sense.
Ring Ni Kakero solidified all the "Jump cliches" and ignited the magazine's popularity (Jump circulation in 1974 was 1.65 million, during 1977 (the year Ring Ni Kakero started) was 1,8 million (So in 3 years it had "only" gained 150,000 new readers... :/), its circulation in 1980 reached 3million, almost a 100% increase in the span of 3 years during Ring Ni Kakero's popularity peak.
.
Dr. Slump perhaps the biggest Jump anime (According to TV ratings) achieved something only that series did which was
get the most popular Jump anime which even lead to the wildspread use of the N'cha greeting used in the series (this was in the 80s of course probably no one does it nowadays lol).
Then Dragon Ball came and funnily enough you could argue that both series pretty much had the same level of popularity in Japan (Manga sales per volume reflect on that) but outside Japan
Dragon Ball did something probably no other series will ever do, which was shape an entire generation across the globe, something that I don't think can be repeated now a days, at least not for an anime, there's no one in my generation here in Mexico who doesn't know who Goku, Seiya or Oliver (Tsubasa Ozora from Captain Tsubasa), this happened pretty much in every country, except for english speaking ones... Weird... I know for English speaking people is hard to understand, but I'd say is similar to how everyone knows who Mickey Mouse or the Simpsons are, but the level of attachment people have for these characters is way bigger than that you have for Mickey or the Simpsons I'd say haha.
Then One Piece came and it outsold Dragon Ball, but that's not it biggest merit, I think. Sure magazine sales have declined over the years, that's expected, paper is dying but
One Piece not only thrived but succeded and became the most epic story of all time, Ok I may be exaggerating but to me it is lol, I guess One Piece achieved being the best selling manga ever, but I also do not think that's it biggest merit, I think that perhaps One Piece has not yet reached its true final "merit", think about it, it's very close to beat Batman in sales, then there's Harry Potter (500million copies sold IIRC) and then Superman with 600million... So perhaps One Piece will get to be the best selling literary fiction of all time? Who knows.
Then we have Kimetsu No Yaiba... Yeah.. Ummm.. I guess I don't really know what to say about it other than it proves that
NPC mentality is a thing lol..
/s
Yeah I'm being salty but meh,
The fact I didn't even mention Shaman King, Hunter x Hunter, Rurouni Kenshin, Dai No Daiboken or any other romance manga is proof there are and will be too many popular series and from different genres that appeal to different readers.
A decline in print magazines is expected, but I think there will still be manga that get crazy sales... But Japan's population is slowly declining, so who knows.
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Other example is when I finished watching FRIENDS I though heck.. I don't think there's a show that I'd love as much as this one and then I watched How I met your mother, and I liked it just as much if not more than FRIENDS (again, no arguments here it's just my opinion) but then HIMYM ended.. And then I loved Community and now I watch Brooklyn909 which is fine lol.
Same for drama television, back when Breaking Bad ended I thought.. Yeah nothing is gonna be better than this and then came Game of Thrones which for a long time was great until... it wasn't.
Point is there will always be new and exciting new things to read/watch
