With the announcement of Shenmue III coming for PC on Unreal Engine 4, it'll be interesting to see in a few years what mods the community will make. It's already really impressive what the community has managed to do with the Dreamcast games, but now that process will be much simplified. Even without an SDK, fans have come up with great mods for GTA V on PC.
Maybe some people will start a Shenmue I and/or II remake based on the assets? Add arcade games? Update the textures to super ultra mega HD in 2025? Even though it's so far away, I think having Shenmue III officially on PC will really help with the game's longevity.