I also wondered about this and was set straight by someone from the discussion forums at Apple. FCP (and DVDSP) do not need QT Pro to function. Yes, I know QT Pro keys are bundled with both applications, but that only effects the QuickTime Player on your machine.
If you don't install the QT Pro key, you can still export to all QuickTime formats (NTSC DV, MPEG4, Sorenson Video 3, etc) from FCP, you just cannot access the advanced functions of QT Player (setting in and out points in the players, downloading movies from the web).
That being said, I'd gather that FCP 5 (or whatever it is called) will shipped with a QT 7 Pro Key.