It's certainly possible, but I'm hoping Suzuki and co. are already in pre-production on S4, I would hope/expect development to be well under way by the time UE5 releases next year especially if:
If they change to UE5, you can absolutely forget about a 2022 release date, that's a 1 year turnaround after porting to a new engine. Unless nothing breaks and everything works perfectly (which happens all the time in game development /s): that's impossible. 1 year out from release, you're starting to ramp up press releases, trailers, etc. not changing the engine.
I'm just speaking from experience having actually gone through this process. Game development, even for small teams, is a very slow moving ship when you actually have deadlines and budgets and publishers to answer to.
Another thing to consider is, the further the release date is pushed (say 2024), the more Shenmue runs the risk of looking even worse by comparison. 4 years from now we're going to be getting the latest Naughty Dog and Rockstar games showcasing the power of next gen consoles. If Suzuki really wants to court a new audience, that's going to be tough to do with such stiff competition. Lots to consider.