First, to argue that web application need to be "on par" with Desktop applications to replace them is totally false. See The Innovator's Dilemma. In a nutshel

First, to argue that web application need to be "on par" with Desktop applications to replace them is totally false. See The Innovator's Dilemma. In a nutshell existing technologies become too feature rich and complex and exceed market demand. This creates a disruptive opportunity for simpler technologies to replace them in the mainstream by growing upmarket. When disruptive technologies achieve the minimum required feature set to meet market demand, market competition shifts to other criteria. One case study in the book describes how cable actuated earth movers companies felt save as hydraulic actuated earth movers could never move as much earth and initially had zero commercial applications. They still can't. Yet hydraulic actuated earth movers have almost completely replaced cable driven ones, except at the market edges that require extreme performance, by establishing a foot hold beneath the existing market (ditch diggers) and innovating upwards. Web applications are simple compared to desktop applications. They are constrained by web standards and run in sandboxed environments. The question is not whether web applications can exceed Desktop applications but whether they can meet market demand. Software + Services (a term Microsoft created when faced with the Internet Services Disruption) is a hybrid, transitional strategy for desktop application companies that makes sense in partially connected environments. This is the model of Dropbox and every other data replication provider. Over time, perhaps with ubiquitous 4G networks, we'll see how this fares against low maintenance operating systems and zero maintenance web applications.