NVIDIA and CD Project Red announced that The Witcher 4 will get the RTX Mega Geometry extension. It runs on Nanite, a hardware-focused method for handling very dense model geometry, and is meant to raise fps while lowering VRAM load.
Benchmarks from Alan Wake 2 show fps uplifts in the ~5–20% range and VRAM savings of roughly 300 MB versus running without the feature. So, RTX users of The Witcher 4 should expect similar or—depending on your GPU, resolution, and scene complexity—even larger gains, though real-world results will vary.