My main concern is the gameplay and the ability of the team to renew it. I'm not sure if I can appreciate the QTEs like I did in the 00's. Apparently, Yu is aware of that and wants to evolve the system to another level.
Will Shenmue III reach the brilliance of the catching leaves ? What would be the gameplay if Ryo has to strike something like a rock or a tree again ?
Video games still use pad and buttons after all, it's hard to invent new things and Shenmue use a concept where constant gameplay innovation is needed to not bore the player.
My other concern is the length of play. Shenmue was fun because you could play tons of mini-games, do some interesting side quests and unlock some other events. It's more a question of things to do rather than the open world scale.
As sure as I will appreciate and love the game, I expect some awkward feelings, the kind of bitter taste you experiment only after the end of your playthrough. Hopefully it will only concern minor parts like make a better fortuneteller than Ailian He (hard task !).