Aren't they already for big (desktop/workstation/server) chips? I'd say Zen3 is the state of the art in that market and that uses a mixed process. The IO dies are global foundries 12nm for AMD.
The mobile market cares more about efficiency than easily scaling up to much bigger chips, so the M1 and other ARM chips are probably going to ignore this without much consequence for smaller chips.
Intel still tops sales because of non-perf related reasons like refresh cycles, distrust of AMD from last time they fell apart in the server space, producing chips in sufficient quantities unlike the entire rest of the industry fighting over TSMC's capacity, etc.
