DLSS3 Frame Generation does not and probably will never work in VR. The ordinary DLSS (upscaling) works in VR both in 30xx and 40xx series GPUs. There are not significant improvements to “ordinary DLSS” in 40xx GPUs, 40xx series is just generally faster and less power hungry vs. 30xx series. For example 4070Ti performs more or less like 3090, however 4070Ti has less of VRAM which affect performance negatively in some cases.