Ken Kaneki is going to die in the third season run of "Tokyo Ghoul." This is one of the persistent rumors about the long-delayed season of the anime that has left the fans wondering on its veracity.
In the absence of any official release from people behind "Tokyo Ghoul" season 3, fans have come up with various speculations and rumors that may later be proven true or otherwise once the third season of the anime has already been released. However, there is no denying that one of the most disturbing rumors about "Tokyo Ghoul" season 3 is that Ken Kaneki will be killed off.
However, according to reports, there is no truth to the rumor and speculations that the anime's protagonist will die; rather, he will just lose his memory. This recent report is supported by a forum on Stack Exhange more than two years ago, wherein avid readers of the manga counterpart of the anime exchanged opinions on what might have happened to Ken Kaneki in his fight with Arima.
As it is also rumored that the anime will stay faithful to the manga origins of "Tokyo Ghoul," it is unlikely for Ken Kaneki to die as he was not killed off in the print version of the story.
Apart from the rumors that Ken Kaneki will die and lose his memory, there are also speculations claiming that the upcoming season of "Tokyo Ghoul" may actually be a reboot of the whole series. While the first season of the anime was lauded, the same thing cannot be said about its previous season as the events in the anime deviated from how the story was told in the manga. Needless to say, it left the fans disappointed, hence, allegedly, the decision to reboot the whole series.
However, as there is still no official word from the makers of "Tokyo Ghoul," everything is just a speculation at this point in time. If the anime will, indeed, be released after its reported live-action feature comes out, only by then the things mentioned earlier can be confirmed.