I think the begining of Shenmue 3 will take place in the cave where the sword and the magic stuff occured.And i think Shenhua Ryo will leave the cave and Ryo will ask Shenhua "Do you have any idea where your father might be?"and Shenhua will answer "no" and then Ryo will tell Shenhua the reason why hes in guilin and they will both togehther go search for Lan Di they will find Lan Di RYo will kick his ass then in the next Shenmue games discover the mystery of the mirrors.
Just a theory ;)