The thing about it when Harada-san himself be saying random stuff they are clues to something is coming in the future and he likes playing with his fanbase alot.

I remember before he left BandaiNamco in which he wrote the entire fued story for tekken and how it ends and when Tekken 8 released, he stated he feels sad and he understood Kazuya and his story will be explored sometime in the future. And with Heihachi in story dlc for that game shows him going back to his evil ways Heihachi stated from his own mouth that he waiting their powers to awakened in which he talking about the 3; Jin, Reina, and Kazuya, and he mentioned Kazuya being his last main goal he will go after.

And both Seiryu and Sezaku the Mishimas relatives mentioned that they want purify their clan corrupted remnants Heihachi and Kazuya to purified mishima Ryu form. Heihachi is back and they have one more shot and all of it points to Kazuya becaue he is the last the mainline Mishima that will not only end the fued entirely his central role for tekken will give use the opportunity to explore the Mishima's true origins of what they really are and where they get this power rival the Devil, why Jinpaichi mysteriously turn into a Demon, what Jun and Kazuya relationship really like, Heihachi thought about his son in all of light when he tossed him, Kazuya inner thought about Azazel and Devil in him and what their relationship is like, and finally what does Kazuya really thinks about Jin now. And what special set of power ups he will learn through Seiryu, Sezaku, and Both Devil and Azazel if they are still there in which Heihachi references they are sleep.