How high they can go really depends on the process. TSMC 7FF silicon didn't go that high early on, max clocks really were improving as the process matured. This was very noticeable with AMD Zen 2, early dies topped out at ~4.2 (for all cores on the die), later ones often easily take ~4.4.
How high it goes also depends on the CPU design. We know TSMC's 7NM can make CPUs that hit 4.5ghz, the Ryzen 5000 does this. It's also quite likely that TSMC's 5nm can still hit the 4ghz+ range in a CPU application.
What we don't know is if the M1 can actually run at those frequencies, too, or if there's other bottlenecks that prevent the M1 from clocking higher than it does.
How high they can go really depends on the process. TSMC 7FF silicon didn't go that high early on, max clocks really were improving as the process matured. This was very noticeable with AMD Zen 2, early dies topped out at ~4.2 (for all cores on the die), later ones often easily take ~4.4.