It kinda feels like the whole drama of kyoukai using the forbidden technique has been ruined. First it was 'if you use this, you will never come back', then it was 'you can come back, but you'll have a reduced lifespan' and now it's 'you have a reduced lifespan, but your lifespan was already really long so you now just have a normal lifespan'. It feels like her 'dramatic sacrifice' has lost both the drama and the sacrifice.
I'm quite excited to see who becomes the new great 6. We already have 3 in Moubu, Tou and Yotanwa (technically she isn't a great general but I presume she'll be included).
Ou sen seems a pretty obvious choice for number 4 (his achievements in the latest campaign outshine his ambitions imo)
Kan Ki will probably take number 5 (Another case of his skills being so good that they can look over his personality)
That only leaves one spot. I doubt they're going to give it to a nobody or someone who isn't a general, which leaves Shin, Ou Hon, Mou Ten and Heki from what I can remember.
Ou hon hasn't done a whole lot recently so I doubt it will be him
Mou ten is in the same situation as Ou Hon
Shin has had a lot of recent achievements (namely killing Houken), but he's also had quite a few failures, failing to win against much weaker opponents without the help of Ten or Kyou Kai. Also plot-wise, I don't think Shint getting promoted here makes sense.
Heki seems the most likely imo. He's been in the game the longest, he had big achievements in the Zhao campaign and he's a very solid general overall, although he doesn't really have the confidence or strength you'd expect from a great general so idk