Bleach hasn't even gone as long as Naruto or One Piece.... How is it "that one" manga? It's been organized into pretty clear story arcs from the beginning, so it had to end with one of them /eventually/.
If you really want "that one" manga you never expected to end, it'd be Kochikame.... It's a gag manga in the first place with no "long" character-driven story arcs and characters that don't seem to age. It will go on until the manga-ka dies or gets too ill to continue.
While it's the final arc, it doesn't means it is ending anytime soon... not before 5 years atleast. Kubo takes dozens of chapters for useless and annoying stuffs, and we know how dragged out the fights in Bleach are no matter who the character is. Kubo has tons of annoying characters to deal with... 200 chapters would be the least amount to end a never ending work like Bleach.