Shenmue was released, what, 10 years ago now? Perhaps in development since '96/'97 (the Saturn version I mean), the people who worked on the game are not getting any younger. Ideally if we wanted a sequel, we would like the same team behind the orginal two games. However can't really see the original team getting back together again for a third game. I would hazard a guess that several of the people on the Sega-AM2 team from that time have been reshuffled, changed jobs, or retired completely.
Hypothetical scenario; Shenmue 3 goes into development. A new team at Sega is formed under the supervision of some of the senior members from the time of Shenmue 1&2's development. It's written and directed by Yu Suzuki (who has had many years to reflect on the mixed reception to his Shenmue dream). Ultimately, trying to please several audiences at once, and unable to capture the same essence as the late 90's-era AM2 did, the game sucks. (I know I'm speculating a bit, but think of the disappointment associated with something like Star Wars Ep.1- unless you liked it.
) Maybe now it appeals to more audiences and sells much better, but it's just not Shenmue.
So what I'm getting at is- is it too late for Sega to make this game? Would it be nicer to enjoy the experience with a sense of nostalgia, rather than frustration on how it got ruined? Or would you want it, no matter how it turns out?