Shuttleworth made the announcement writing:

As part of our planning for Natty+1, we’ll need to find some space on the CD for Qt libraries, and we will evaluate applications developed with Qt for inclusion on the CD and default install of Ubuntu.

Ease of use, and effective integration, are key values in our user experience. We care that the applications we choose are harmonious with one another and the system as a whole.

Of course, the developer’s choice of Qt has no influence on the first two. Qt itself has been available under the GPL for a long time, and more recently became available under the LGPL. And there’s plenty of best-in-class software written with Qt, it’s a very capable toolkit.

More at http://www.markshuttleworth.com/archives/568