After Eastern A/L bought their firs A300s, the possibility of a Twin Ten was studied seriously by McDouglas, but there was never enough customer interest.
The rightful semi-retirement for the DC10-30 and MD-11 is conversion to military refueling tankers, where fuel economy isn't such a big deal. The KC-10A has always been the most reliable plane in the USAF fleet.
Tankers get about a tenth the utilization of airliners, so it is extremely wasteful to buy new tankers such as the KC-767 or A330 equivalent, when half-life airliners are plentiful and cheap.
GB