The open source browser Firefox is going to lose its market share for the benefit of Webkit rendering engine based browsers. Firefox came up in a time as Microsoft's Internet Explorer was not improved for years. Despite many user requests Microsoft was not willing to implement the nowadays omnipresent and revolutionary "tab feature". People started to look for free alternatives and found the Mozilla browser (turned into Firefox) which had this coveted feature.
However the technology base of Firefox is quite cumbersome and not really suitable for RAD. As a result of the approach to develop a browser, Apple took the open source rendering engine KHTML and made webkit which is the (quite fast) rendering engine of Apple's Safari browser. As Webkit had to keep the LGPL this rendering engine can be used in other (also closed source) browsers. Furthermore Webkit has a much cleaner and better readable code than Firefox' Gecko engine and is going to be adopted by Qt4 (and therefore also the Konqueror browser) as well as by Gnome's niche browser Ephiphany.
There are plans to port KDE (and therefore also Konqueror) to Windows and in fact there is also a working alpha release of Konqueror which is running under Windows. Without any doubt and without being prejudiced Konqueror offers the better user experience because it looks better, feels snappier and have a cleaner code base than Firefox. Also there is a working beta 3 release of Safari for Windows. Moreover Internet Explorer 7 is not that bad as its predecessor and is much better integrated in Windows than Firefox.
Hence there are decreasingly less reasons for using Firefox under Windows and Microsoft's Windows has a monopoly on the desktop market. Thus if Firefox' market share on Windows machines goes down also its overall market share will significantly slim down.
But Firefox is currently Google's browser of choice... but for how long?