Is the next chapter going to be released with this update? chapter after Hermes leaves?
No, but they are the next after this one. Chapters 19 and 20 will come out together.
so this means the next update will be the complete full circle of asterion's plot?
It will continue Asterion's story. We're about two thirds of the way through, there's still some stuff to cover. You can think of it as the beginning of the final stretch of the game.
When will the chapters 19 and 20 be released out of curiosity, roughly?
When they're done.