For those still waiting on a PS5, I doubt the 4th Shenmue would be exclusive (gen-wise) to it. I'm far more willing to bet it would be on PS4, PS5 and PC. No way the publisher would miss out on an install base of 120 million units on a more niche series.
Regardless of that, don't feel like you're missing out because you don't have a PS5. There's maybe 5 exclusive games on it after a year thus far and none are really up my alley. There's almost no point in owning any of the next systems yet. The only upgrade I feel I got was load times. Everything I'm playing is also on PS4 or even the PS4 versions.