Since Sept. '08, Hasselblad has come under fire from both it's customers and the industry for not providing a buy-back upgrade path for owners of previous models.  An interview and statement from Hasselblad can be found at the British Journal of Photography's story, here, but the details of a part of the upgrade program to the new H4D system are found on the Hasselblad site, here. 
 

The big print- :
"All units purchased from September 25 will be upgraded to H4D-50 free of charge. H3DII-50 to H4D-50 upgrades will be done in Redmond starting January 2010. H3DII-50 purchased from September 25 have the option to upgrade to H4D-60 for $8,000 (difference in price)"
 

No doubt there's some fine print too...  contact your dealer for more information, but if you've been waiting to pull the trigger or you did pull the trigger in late September/early October, you may be covered.