I was browsing threw the Pitivi wiki and I found this doc -> http://www.pitivi.org/wiki/Design_Docs_Plugins
It says on the bottom "This page was last modified 12:36, 29 August 2007."
WTF!!! You've been talking about plugins since then and still hasn't decided how to do it???
ROLL A FRIGGIN DICE DAMMIT! :P