Salut,
Il semble que ce soit possible (cf ci dessous). Une precaution serait de demander explicitement l'annulation du WHV au cas ou ton expatriation se realiserait.
@+
My travel plans have changed and I only want to enter Australia as a visitor, can I change my visa?
Yes, if you apply for an e676 tourist visa, your WHM visa will be cancelled.
You may re-apply for the WHM visa again as long as it has not been used to enter Australia.
Note: If you wish to obtain an ETA (electronic travel authority) for a short visit, you must contact the WHM helpdesk to cancel your visa before you can enter using the ETA. The ETA will not come into effect until the WHM visa is cancelled.
Source
http://www.germany.embassy.gov.au/beln/WHM_engl.html