A new leak says the Dimensity 9400's GPU offers a 61% performance improvement over its predecessor. It even manages to outperforms Apple's M4 SoC in the GFXBench Aztec Ruins benchmark. https://www.notebookcheck.net/MediaTek-Dimensity-9400-Arm-Immortalis-G925-GPU-allegedly-trounces-Apple-M4-in-GFXBench.892530.0.html
This performance is probably an indicator where 8 gen 4 will be