This title belongs to bleach unfortunately, as for one piece falling out of grace, this is nothing other than wishful thinking.
Oda perfected the shonen formula on top of having an EXTREMELY loyal fanbase, one piece can still keep going on for another 20 years.
Last but not least, there is an important detail that people on this forum seem to forget: oda doesn't own one piece, shonen jump does. If they tell him to keep drawing this for as long as possible, he will.
OP is shonen jump's greatest and most profitable asset who keeps making more and more money, not to mention collectables, toys, vídeo games, etc...
Other thing that i thought about now is: Manga's Golden generation is GONE, comparing nowadays manga with the ones that came around mid 90s until late 00s is depressing.
It's 2022, almost 23 and there is still no other manga with potential to sell as much as the big 3 did, not to mention FMA, death note, Gintama, code geass, soul Eater, etc... There were a LOT of great titles back the, competition was ruthless and we had plenty of options.
OP Will keep going for as long as possible simply because shonen jump KNOWS there are neither mangakas nor mangas able to present the amount of exciting Works they had on their prime(mid 90s- late 00s) therefore, they will stay clinging to the last representative of those golden times for as long as ite gets.