The plan is in the earliest stage and recruitment offers for Qt/C++ developers will pop up soon. Don't expect any Qt application developed by Nokia for the tablets anytime soon, though. The first actual step will be the distribution of the Qt libraries for application development in maemo.org during 4Q2008
Nokia has no plans to offer a "hildonized" Qt-based UI. Qt applications will look different in the tablets just like some successful 3rd party applications look different.