18 months ago I went to an aperture seminar in London. The demonstrator was talking about the ability to provide this feature in the future.
It would be very useful to be able to use a number of the plugins that I use in CS directly in Aperture or Lightroom. However I do not think that we will see the serious offerings, like Photokit, Noise Ninja etc, as Aperture plugins in the short to mid term - if ever!
IMHO I agree with the above post about offerings such as frame borders, effects and film emulators etc,