It's just too early to discuss about compatibility across Fremantle, Harmattan and corresponding hardware. Some elements for discussion are not public and some elements are not even known by anybody today.

These elements include the state of Maemo 5 Qt bindings compared with the Harmattan API, the existence of a community initiative to maintain GTK+ / Hildon beyond Fremantle, the characteristics of the hardware to be released during the Fremantle and Harmattan releases...

There is even another element, which are the alternatives to the Hildon/Qt native environments. From the announcement this week you can see that OpenGL ES is there, and someone might be interested going that path. Note that we haven't given any details yet about that Maemo API on top of the generic Qt / Qt Mobility API, nor about those supported runtimes mentioned in one of the slides.

The announcement helps developers planning their work for Fremantle having a bit more of knowledge about Harmattan. Let's release Maemo 5 and its related hardware, let's enjoy Fremantle and then let's discuss Harmattan further.