The limitation of the processor frequency is due to the skin effect of the wire, and the leakage on the transistor gate. It just doesn't make too much sense going above 4GHz if you want good power consumption and heat. It is also very hard to make use of more than 4 cores, so I think the future is about energy efficiency and discrete circuits that help without doing all these work in software.
Things like DSP and signal processing, graphic cores, etc off loading from the main CPU, and make 10 hours battery life on a tablet possible. This is where the future seems to be heading, and people start going back to the basic and demand software not to waste processor, and cut down processor for power / battery life. This is why Flash is in trouble (the reason why iOS do not run Flash, it is the power consumption).
Regarding to fiber: everything is already running fiber except the last mile, from your local lawn fridge of your phone company to you, from your local cable provider's terminal to you, and from the cell tower to you. We may gradually see them moving toward fiber for the last mile but it would take a while, at a good cost, if you are willing to pay $50/month for a couple decade. I'm not sure if everyone will pay for it, and at least in the US there will be cheaper alternative (i.e. lawn fridge to your home via microcell LTE that covers only 1 block), or the monopoly would just cap your download to save expansion cost.
Optical processor was talked about for a decade already, when I was in school. It didn't go anywhere because no one wants to pay for the infrastructure to make them (FABS), and it is much harder than they original though, and electronic based transistor is getting cheaper and cheaper, and still is good enough.
