as OS-9 is slowly being replaced by OS-X, we decided not to support OS-9 for long anymore.
Development on OS-9 is much more complicated and slows down any other development for Kontakt or Kompakt. Kompakt for OS-X is now in beta test and we hope to release the update soon. As far as I know, there are no plans to support RTAS on OS-9 for Kontakt. Sorry for that. I personally do have an old Mac G4/350 with ProTools and would love to use Kontakt with RTAS but I think there is no other solution even for me than going OS-X.