I dunno about that, they did cancel Shaman King before (in the middle of the final arc, no less) so immunity isn't by any means guaranteed.
From what I recall, Shaman King cancelation was in part due to Hiroyuki Takei losing the drive to continue the series during that time. Yes, the declining popularity and the anime being axed played a major part in it, but with the author himself no longer wishing to continue the series, they just canned it.
With Bleach, the popularity (in Japan at least) is without a doubt at an all time low, the sales are slowly but surely dropping with each volume selling slower and less than the previous ones, and with it being in its final arc without an anime there is little use to it being around at this point. But at the same time, with Kubo being serialised in the magazine for 14 years, I doubt they would cancel the manga outright unless he himself finds that he no longer wants to continue it.
The most likely outcomes would be that 1)They eventually do what they did with Yu-Gi-Oh and tell Kubo to wrap up the story in half a year 2) move the manga to another magazine (Jump Next or SQ, or maybe even Crown, which would be a good idea to promote them) or 3) have the conclusion be in Jump Plus (which would ease the piracy issue).
We also had Reborn getting rushed to an end. I never really got far in it, but I think Nurarihyon no Mago was popular but abruptly ended after a lot of setup?
Reborn wasn't rushed lol. The last 2 arcs and the chapters in between them only showed that Amano had no idea where the story would go after the end of the future arc. If anything, Reborn was extended beyond its natural concluding point.
Nura was about as popular as a cult hit would be, so even after it was axed it had special treatment to end it naturally outside of WSJ. Bleach might share a similar fate, but maybe when it nears its ending.
UQ Holder volume 5. This has really turned into a splendid action series. Can't wait to see more of Kirie and an eventual anime.
The return to Mahora and Fate vs. Eva were pretty much the highlights of this volume. I'm glad that Ken finally managed to hit what he wanted since the start with this volume.
With that said, the Q&A session with Fate is still bad, except that seeing his declaration of wanting to exterminate all life in the universe never gets old.