Interestingly, the semiconductor industry has thought it was close to its theoretical limits since feature size was measured in microns 40 years ago. Back then, one of the big worries was that we were approaching the wavelength of light used in the photolithography process and that there was no clear path to getting below 1000 nm. I expect that it will always be difficult to see beyond a few years of innovation in this area. It certainly does seem that we will soon need to switch to other materials and forms of signal transport though.