PowerBook: Replacement Parts Missing

Apple is facing lack of parts for repairing under-warranty PowerBook G4 1.5GHz and 1.67GHz, especially the top case (replaced when having a trackpad defect). The production will have to be relaunched, but the new parts are not expected before end of July.
It seems that Apple agree to exchange under-warranty PowerBook units with brand new MacBook Pro unit when asked (at least in USA).
There is also a lack of MacBook logic boards, but the channel is expected to resume much faster.