Choice is always going to be a prominent force in Linux. There will always be folks who are going to write new toolkits and apps and there they will find users who would want to promote it. That is just the nature of Open source.
That being said I think no one really likes to use GTK+ app if they are targeting multiple desktop environment and operating system. Ubuntu's Unity 8 and KDE both are using Qt and Qt is already available on all possible platforms including Android.