Initial gut reaction is that things won't be as absolute as Harley would like us to believe. After all, if it's a Harley parts only kind of world than the user base is captive. And that's Harley's biggest wettest dream.
The auto makers have floated similar ideas over the years. Service would, supposedly, have to be in dealerships because of some technology or other. Exhaust or other emissions systems couldn't be touched outside a dealerhsip. Etc etc etc. But Hooker (for but one example) keeps right on making both engine-back and cat-back exhaust systems and everyone is still happy and (basically) legal.
Things may indeed change some for 2007 (or whatever year). After all, things always change. But the aftermarket is so diverse and agressive and the users demanding enough that it's a good bet it won't stay captive very long; no matter how much Harley might like it.