NVIDIA is only open-sourcing the kernel module. User-space librairies and firmware remain closed source and proprietary.
For comparison, AMD and Intel provide both open-source kernel module and libraries while firmware remains closed and proprietary.
User-space librairies also have a major impact on performance, NVIDIA didn't make a move towards making these open-source. Also, GPU older than RTX 20xx will not benefit from the new open-source kernel module.
While it will certainly improve things for using NVIDIA GPUs on Linux, it's nothing revolutionary.