OK, so we agree that:
1. It won't have new features since it's feature complete.
2. Nothing will basically change.
3. All new development of Qt project is done in QML.
4. New features will be added in QML only. So, if some cool widget comes along in a new OS version, you don't have it Widgets anymore.
For me, it's all but obsolete. If you want to argue about English usage, then that's fine.
1) It can have new features - the are some upstreamed from KDE, and it's just about users coming with new proposals - nobody cames, no new features. Easy.
2) Why would you change something that needs no changing?
3) Lot of efort goes to QML, yes. Why not?
4) Maybe. Nothing prevents you from writing QWidget equivalent of the "cool" QML widget and upstreaming it.
Obsolete stuff is unmaintained. You can rest assured that QWidgets will be maintained and bugs will be fixed.
However, since this module has been under heavy use in the past, its feature complete and needs no new features.
Its still used by hundreds of legacy applications and is in no way 'obsolete'.
[0]http://qt-project.org/wiki/Qt_Modules_Maturity_Level