I recall the estimate for Shenmue was that they banked on it so much to sell units that at the time of release every DC owner would have had to buy the game twice for it to cover its costs.
Unless the game radically has changed from the original I don't see much of a future unless dedicated fans continue to crowd fund them but then the whole Epic fiasco may have hurt that prospect. The original game was like an introduction to the concept of open world games that was new back in the time of the DC but in today's industry we're in an open world golden era and have the likes of GOW, BOTW, HZD, GTAV, RDR2, Nier:A, XBC, Astral Chain, DQXI, MHW etc... The series is facing strong competition in this area to the point where even having the best story in history won't do it any favours in standing out.
To be fair you hit the nail in the head there. Even then, Ocarina and later MM conveyed the open world setting better. Shenmue was one of, if not the best looking game in the industry at the time of its release, something that helped hide some of its flaws. It no longer has that advantage today because of its low budget. However for what Ive seen Shenmue 3 is fan service and it seems to accomplish that. It is unlikely we will see Shenmue 4 though .