I'm pretty sure their called 343i because they're a halo devoted studio and Spark is so deeply integrated into the story, and I do like the idea of Cortana dying at the end of Halo 5 because 343 said that title would have a darker story, so I can imagine Cortana dying, and you do all this crazy stuff to save her, but in the end she still dies and the ancient evil becomes more powerful, that would be very depressing. And then at the start of Halo 6 Chief gets a replacement AI that we don't know of yet.