The M1 laptops already have Thunderbolt 3 which is 40Gb/s and actually faster than PCIe 4.0 x16 (only ~35Gb/s).

Also these laptops have 8 CPU cores (4 high performance, 4 high efficiency) and 8 entirely separate GPU cores. It's a powerhouse of multiprocessing, especially when you consider it's in a laptop that gets 20 hours of real battery life.