They're already binning the M1 between the two models of the Macbook Air; one has a 7 core GPU, the other has an 8 core. They haven't outright said this is due to binning, but it seems very likely. Will probably be similar for upper-end models, but more CPU variations as well.

They're fabbing with TSMC, which has a really established history in high yields. Just think about the A13/A14 CPUs, which are probably the most voluminous single CPU models every fabricated by a company, yet have never been subject to binning to other lower or higher end models. As the chips get more complicated naturally there will be more fabrication issues, so I expect we'll see more binning, but it doesn't look like there's much cause for concern.