The N9 will run Maemo with a "MeeGo" UX. But the (Maemo)MeeGo UX will not be the UX that is going to be used on real MeeGo phones.
Nokia will not encourage people developing for that UX, but will instead encourage developing on Qt and Qt Quick.
This will probably be just fine, but think about all the wasted work: Symbian4 UX wasted, Maemo\MeeGo UX wasted. Strange indeed.