From Popular Science:

While that number largely consists of PCs – there are some 1 billion connected in the world that connect to the Internet regularly – and mobile devices like smartphones, future growth will be driven by machine-to-machine technologies like smart grid-enabled appliances, e-book readers, public safety systems, traffic and parking control devices, sensor networks, Web-enabled TVs, and automobiles that sync up to the Net. IMS also projects that by 2020 there will be 6 billion cell phones in the world, most of which will have Internet connectivity.