Dusseldorf is a tricky market. It has a huge population base, but airlines's haven't been able to make regular trans-Atlantic service work. Dusseldorf has had tons of trans-Atlantic service to dozens of North American airports since the late 1980s, and the only city that has had continuous non-stop service to Dusseldorf in the past twenty years is Miami. Air Canada, American, Continental, and United have come and gone. Flights to Dulles, Chicago, Newark, JFK, Denver, and Phoenix have come and gone as well (and in some cases come back).

It is definitley a risk for Delta, but a risk worth taking, IMO. I think they stand a shot.