Correct me if I'm wrong here, but isn't that one of the big appeals that Maemo and the tablets have always had; the only difference was anything that was GNOME/GTK, instead of now anything that's QT, so I don't really see how this a "Game changing" development or is going to make native app building any better or worse in theory... I haven't used both extensively, but the impression I get is that QT is much more mature and broad than GTK, but that really doesn't change the fact that both provide the idea of "you can develop natively regardless of your IS devel environment and port anywhere else with a re-compile"; after all, a huge chunk of the apps we have on the tablets right now are simply native Linux apps that have been recompiled for ARM using the Maemo SDK...
That aside, I'm still very much looking forward to the next device and software, and I'm sure there are lots of great changes that are happening, but I don't see your point of QT suddenly changing everything in terms of development... maybe in the long term, but based on the way Nokia treats things I can still imagine lots of odd and unexpected roadblocks to be crossed before we really start to see any major benefits to development processes; I'd argue that things like a well rounded Python package have had a MUCH larger impact on the availability of apps and features than anything else at the moment (and I'm not a big Python fan, but the point remains)