<QUOTE>Most applications today are written for Windows, PS3, Wii, iOS or Android. Not for X. Developers know toolkits (mostly GDI, but sometimes WPF or even Qt) and DirectX/OpenGL. They don't know X and then don't want to know X.</quote>
As an application developer with over 10 years of experience, I can say with certainty that this is not true, at least, not for me.
I don't write applications for Windows, PS3, Linux, Android, or *any* of the platforms listed. I write for the web browser! I write complex, data-driven applications and it's been a very, very long time since I wrote anything that wouldn't easily work on Win/Mac/Lin/Android/Iphone/Xbox and anything else with a reasonable browser.
The browser I most target is Firefox since it seems to be the most "Cross platform" although Chrome is close. I develop on Linux, it runs FF well, I don't worry about viruses and stuff like that, and can offer excellent compatibility with all my clients.
I don't want to replace X - I get the best of all possible worlds by making the specific rendering requirements of my applications something handled by the context of the user. And I use network transparency all the time - I can run several Firefox instances concurrently, on the desktop, as different users, without any danger of cookie or session interaction between browsers. As a web-based, network application developer, this is so incredibly useful!