Nvidia hasn't ruled out enabling DLSS frame generation on older RTX graphics cards "in the future," but we have our doubts it ...
While this is essentially just speculation about future possibilities, there's a chance that Nvidia RTX 3000 series users could get the full package of DLSS 4 that includes Frame Generation.
Now that NVIDIA has changed the architecture of DLSS Frame Generation, it could theoretically work on RTX 30-series GPUs, but ...