If the new author killed Naruto or Sasuke, i bet the audience would decrease substantially. It's hard for the previous Naruto fans to enjoy a manga who's supposed to be a follow up story without their main heroes around. The new author would be basically putting himself in a weird spot if he wanted this new series to succeed.
People disliked The Last because Sasuke got little to no screen time at all. And Boruto was a huge success because both Naruto and Sasuke were there.