Sooner than later the effects at the particle level are going to begin wrecking MAJOR havoc on traditional semiconductors and the engineers determined to make them smaller and smaller...
They are already having to deal with quantum tunneling. We're reaching the limits of what is possible to fab using non-quantum effects. Already clockspeeds and die sizes have bumped up against the speed of light. i.e., the chip is running so fast that the clock signal that keeps everything in sync can propagate no faster than the cosmic speed limit, so it would take too long to reach the other side of the chip for the clock to stay in sync. It's amazing when you think about it. Once you bump up against certain limits, they'll have no option but to figure out a way to build the chips in 3 dimensions. (I think they are already doing this to some extent)
From a performance standpoint, how much do you really need? My desktop is about 7 years old now, yet from a performance standpoint I can't really justify upgrading that much. Yeah, I can get more cores, but 95% of the time, most of what I have is just being wasted. I've run up against few processes that can really max my box out, but they are few and far between. So, while I wouldn't mind building out a new box, I can't really justify it from a sheer performance standpoint. I've upgraded the hard drive and video card a while back, but I figure I'll give it another 3 years, then I'll put together a top of the line box again, and will expect it to last about 10 years as well. I'm sure I'll see a performance gain, but it won't be anything like when I was moving from one generation to the next back in the day.