Is it possible for the Kyushu ben and Old Eastern Japanese to stay to be different as in stay as a different language instead of Kyushu-ben being in a process of being slowly eaten by Modern Japanese and Old Eastern Japanese already has been merged with what is now Modern Japanese completely , I know since Okinawan is considered as a separate language and Hachijo-ben which is very similar to the Old Eastern Japanese which survives in isolation in the Hachijo islands in Japan which is considered an endangered language as well.