While perusing delta.com, I found this little tidbit:
Source: SkyMiles/WorldPerks Integration Timeline
August 2009
Announce the 2010 SkyMiles Medallion/Elite program details and tentative launch date of a new domestic SkyMiles co-branded debit card.
IMHO, I think this will probably be issued by US Bank in order to deal with having the WorldPerks Credit card not compete with American Express.
This should be good for those of us that prefer using Debit Cards for their purchases in this time of tight credit availability!