TA, Yu has said a few times already (once in an interview with Kenji from Shenmue Master, and again in the postmortem), that Ryo will lose the will to revenge. You can see that even in the first game, although only slightly. The first conversation you have in the game that isn't a cutscene is with Fuku-san, where Ryo angrily says he is going to take revenge. By the end of Shenmue I, he is a bit more calmed and rational (not by much, admittedly), and by Shenmue II is over, he is further along that path. The fight with Lan Di in the future will come out of necessity, not revenge.
Shenmue is much more than a revenge story. The people that say it has a bad story, I feel don't understand the game they are playing.