Finally, we have a development version of Qt 4.7 that can be installed to Symbian^3 devices like N8 and C7. It's meant explicitly for development purposes only and cannot be used deploy Qt 4.7 based applications to Symbian^3 devices. This is the real Qt version and it will actually replace Qt libraries on your device (don't worry, we will provide also a package so that you can revert to Qt 4.6.3 which actually ships on N8 and friends).
Target is that developers can start deploying Qt 4.7 based applications for Symbian^3 devices in Q1 2011.
You may wonder why for development only and not deployment? There are many reasons for that:
There are applications done by both Nokia and our partners that are based on Qt 4.6.3 and which will ship on Symbian^3 devices. We must ensure that when upgrade to Qt 4.7 is done, those applications will still work - that's the compatibility promise we have given and that's a strong one. And the same applies to your Qt 4.6.3 based applications built for Symbian, so if you run into issues here, please let us know - http://bugreports.qt.nokia.com/.
We want to ensure Qt 4.7 for Symbian^3 will provide a smooth platform for QML and Qt Quick - believe me, it is already now awesome but there are still some improvements we want to do.
We want to also improve the multimedia related capabilities of Qt on Symbian^3 devices. We know that there are some issues and we are working hard to fix those.
You may wonder why we didn't create a "system Qt" and allowing deployment of multiple Qt versions by applications? We want to ensure as efficient usage of system resources as possible and that all applications will benefit when an upgrade is done. In the long term it would not be sustainable if you would have different versions of Qt installed to same device depending on what version some specific application would be depending on.