We hit that wall 20 years ago. That's why we went parallel. It's not just extra cores that are more parallel, extra instructions get their performance from parallelism, too. They allow an operation to be simultaneously performed on every entry in an array much quicker than would happen with a loop performing the instructions one at a time. Caches also not only get bigger, but also wider, so a single fetch brings in more data.

The physics of the gates isn't the limiting factor. They only work because of quantum effects, so they keep working as they shrink, although the voltage does need to decrease to limit tunneling, but it also gets to decrease because of the thinner oxide layer and lower capacitance, and that allows for increased speed and reduces power consumption.

The limiting factor is manufacturing at that small of scale, with light wavelengths being too large for etching features small enough to shrink transistors further. ASML is the only company that makes current-generation extreme ultraviolet manufacturing equipment, and researchers are looking into using X-rays or mechanical stamping, for future generations.

On top of more parallelism, recent gains have come from better packaging, with 3D stacking shortening the distance signals need to travel, allowing busses to operate faster. For example, AMD's X3D processors couldn't have as much cache as they have if it were manufactured on the same die as the processor, unless they slowed it down, which would be counterproductive. It does limit heat dissipation, but it also reduces heat generation, because the busses don't need to be driven as hard, so it's still worthwhile.

We've also made a lot of gains from better transistor geometry, with increasing ratios of gates to channels, creating a larger difference in resistance between on and off states. If we can keep shrinking manufacturing processes, even to the point that we design to the nearest atom, we'll be able to use that precision to keep creating better geometry, even though the transistors aren't meaningfully smaller.

One thing is for certain though, even though current processors only work because of quantum effects, when AI is no longer the peak buzzword, quantum will come back into vogue as the snazziest buzzword, and future generations of processors that are just a regular evolution of current technology will be marketed as quantum processors, despite not using qbits or quantum annealing.