Apple is EXTREMELY paranoid about releasing APIs which turn out to be
unsuitable. To Apple, an API is a fairly ironclad contract. A public
API says, "We will support applications which use these calls for as
long as we support the platform that they run on." If the API ends up
doing things badly, they're stuck supporting it for a very long time
anyway.
As such, they like to make private APIs first, see how they work, then
redo them based on their experience before they make them public.
I personally think they're a little too paranoid about this stuff, but
overall it's fairly well justified. Especially for something like a
plugin interface, you don't want to release your first attempt at it,
discover that it's not very good, but then be stuck supporting it for
ten years anyway.
Is there a user-facing consequence to not having a QTX plugin API
available yet? A lot of people are asking about it, but it doesn't
seem like it should matter to me. QTX the application will happily use
QT7 components for playback, so Perian still works fine.
Mike