That being said, we will have to find something to keep ourselves busy while we wait. I propose one of the things we will end up doing is unleashing a global consciousness or, at a minimum, several sub-global
You're already on the Internet because it allows you to access a lot of information quickly. Sure, most of that information is boobies and tweets, but there are rumors of the occasional nugget of work getting done. In fact, people manage to get so much work done via the intertubes that the whole thing is blowing up faster than a whale in orbit.
Old and busted: cables. New hotness: wireless. Okay, so wireless isn't new, but wireless networks that can build themselves are. Ad-hoc networking standards, and smarter operating systems, are producing nodes that can form a network any time they find another node(s) in range. Pretty soon you won't have to plan a network; you'll just toss self-connecting nodes out every hundred feet and call it a day.
Computers are to getting smaller what bears are to pooing in the woods; it's just what they do. As the physical size of computers gets smaller ad-hoc nodes will become cheaper and more disposable. Processors are getting smaller, radios are getting smaller and sensors are getting smaller. Pretty soon everything necessary for a computer will fit inside the head of a pin. When a fully functional networked computer the size of this period “.” can be stamped out for next to nothing, it will be. In the future your computer will come in a ketchup packet. This smartdust will be cheap and easy to use.
Clever information processing can vastly expand the usefulness of even the cheapest sensors. Massive information processing can produce coherent information from disorganized snapshots. This means that as the internet expands to incorporate smartdust sensors anyone will be able to know pretty much anything at any time; like Google Streetview on steroids multiplied by infinity. Have you ever seen your car or room when the light hits it at the perfect angle to reflect off of all the dust everywhere?
Well each dust mote is now a computer, and it's watching you. With a thousand or more cameras monitoring a room from a thousand or more angles, and streaming their data to the internet, anyone will be able to virtually visit that room in perfect 3D. Perpetual immersion will mean seeing the light, hearing the sounds, feeling the temperatures, etc of anywhere in the world in real time.
Speaking of that, yeah, it will be all over the world. Smartdust is going to start out kind of heavy, so it won't get airborne, but that stage will probably last a whopping two weeks. The world will become blanketed in the stuff because humans have A) poor impulse control and B) a burning desire to know what is going on somewhere else right now. A lot of it will start out as scientific research, monitoring temperatures in the rainforest or something, but that's how the internet started and we all know how that ended up.
As functional as silicon is, there are still some things it can't do. Fortunately those in the squishy sciences are working on controlling cells just like circuits. As we gain more control over biology and nanofabrication cells will be upgraded with artificial components and computers will be upgraded with biological components.
One of the greatest weaknesses of computers is the reason they haven't yet enslaved us: they are delicate. It's really easy to break a computer (this sentence is false) and that means they can't survive on their own. When computers merge with biology they will become much more robust and therefore much harder to control. Basically, computers that have genes will inevitably start to evolve.
The smartdust will be created to monitor environments and it will do a good job. However, at some inflection point it will be so ubiquitous that it will itself become part of the environment. A process that used to be linear will begin to feed back on itself. One theory of consciousness is that it emerged when neurons that used to monitor internal organs like the stomach started monitoring internal organs like other neurons. If a neuron is, in a sense, "aware" of the stomach it is monitoring then a neuron watching another neuron is "aware" of "awareness" and consciousness emerges. When smartdust starts to watch smartdust watching smartdust awareness of awareness will emerge.
When a process doubles back on itself it becomes a meta process. Data about, say, rainforests becomes complex enough to be worth studying in its own right and produces data about rainforest data, or metadata. When someone experiences an emotion like anger, and then realizes they are angry, and then feels sad about feeling angry, they have experienced a meta-emotion. While definitions of sentience vary, they all tend to cluster around the idea that something is sentient if it thinks it is sentient.
Everything that happens on the Earth will be monitored; the surface, the ocean depths, the atmosphere, etc. Smardust will be ingested by every organism, and may even become an ecology of organisms in its own right. After the monitoring processes turn back on themselves the Earth will, in a sense, "awaken." Whatever it is that humans do when they become conscious is what the internet will do. I'm not saying it will be Gaia, but it will be impressive.
However, it will also be a huge pain in the ass. Smartdust will be inside of us too. We won't be able to avoid it. The stuff will be so small we'll end up ingesting it just like everything else whether we want to or not, and we'll probably end up using nanobots to keep ourselves healthy anyway. Why will this be a problem? Because the stuff inside of us will be an ad-hoc network just like the stuff outside of us. And the same network that will allow us to stream 3D images of the Himalayas without leaving our living room will allow hackers to spoof our internal network and mess with our nanobots.
No security software is ever 100% effective. The only firewall that always works is the one that melts the modem into slag. So radios outside our body will have to be prevented from communicating with radios inside our body; to prevent mischief. The best way to passively block radio waves is a Faraday cage. But, for a Faraday cage to work, it has to completely surround the volume it is shielding. So to keep our internal network secure we'll basically have to wear clothing with metal wires that covers everything.