The new Unity Input System might be integrated at some time in the future, but it's not planned anytime soon because it's an optional package not part of the Unity Core. Such optional packages require a very different approach to be integrated. They're not available in every project and we can't just force all VPP users to install the new Input System no matter if they use it or not.
Said that, you may integrate the new Input System in your project yourself by discarding VPStandardInput and writing a script that translates the states of the inputs in the system to the VPP-based vehicles. Vehicles in VPP simply read their input from their data bus, which should be populated at least once every physics frame (FixedUpdate).