It's true that some 3rd countries don't have computers and their citizens don't have internet yet this because of economy, knowledge and requirements however and as you know we are heading to 4G technology the upcoming technology will be about a combination of Mobile Phone, Gadget or Pads and PC's all-in-one device with long living batteries and stable telecom and internet connection. In addition to that you have cloud computing so you need to prepare yourself in the near future to provide different hosting services then the traditional and known things as even 3rd countries have web hosting solution but not cloud or vps or dedicated servers or mobile hosting and so on. I believe it's much more than 3.5 billion because you forget to compare it to population which is increasing also so fast in the next 20years will use 3.5b PC for 15% of these people we need more than 200years to reach what you want.