I have been in touch with W3Techs and the technique they rely on for identifying CMS platforms is very simplistic. For DNN they look for the existence of a specific JavaScript file and while this can be used to reliably identify if a site is running DNN, it can not identify the version. It is for this reason that W3Techs shows no installations of DNN7 and only minimal installations of DNN6. So to conclude that people are not upgrading from older versions of DNN to newer versions based on the W3Techs data is totally unreliable. We know for a fact that people are upgrading - both based upon the upgrade questions asked in our community forums, and the trouble tickets entered into the DNN Customer Support Network. That being said, I understand that people rely on third party sites like W3Techs to judge the growth of technology and I will work with them to ensure that they start to represent new DNN install versions appropriately.

On a separate note, when it comes to both performance and upgrades, the number of core customizations and third party extensions you utilize can often adversely affect the performance of your site, as well as complicate your ability to upgrade to newer versions of DNN. In general you should always try to minimize your dependencies.