In future iterations of Ubuntu (Natty and onwards), Ubuntu CD might ship with Qt libraries - Mark Shuttleworth noted in one of his blog post. 
He further clarifies that Qt applications should not be confused with KDE apps. And if KDE applications are to be included in a default Ubuntu install, they should be able to interact with the dconf system configuration. Unfortunately, as of now, this is difficult as Gtk apps all use a centrally-manageable preferences store, and KDE apps do things differently.
The basic premise behind this announcement is that it is the quality and usability of the application (to be included) that is important; the choice of toolkit should be irrelevant.
Ubuntu till date have shown a bias towards applications built on Gtk toolkit. Currently, almost all applications that are shipped with Ubuntu are GNOME centric. And if a user needs a Qt based application the recourse is to manually install it from the Ubuntu repository.
However, this is going to change in the future.
Mark Shuttleworth further suggests a procedure (see flowchart below) to decide what applications will go into a default Ubuntu install.
He further clarifies that Qt applications should not be confused with KDE apps. And if KDE applications are to be included in a default Ubuntu install, they should be able to interact with the dconf system configuration. Unfortunately, as of now, this is difficult as Gtk apps all use a centrally-manageable preferences store, and KDE apps do things differently.
[Source : Mark Shuttleworth]
