There is enough demand..and even if there isn't, DC10 is cheaper to operate than DC8, so it's a better plane even if it can't be filled.
When you can fill them then yes, but I would not be so sure when talking about 150-200 sold seats.
My records show that DC10-30 is about 74% more expensive to lease than DC8-62/63 (I'm not currently in GW that has both of them so can't check)
has 56% higher MTOW (landing, handling costs)
requires 33% more stewardesses
has 2x longer turn around (harder to schedule, less profitable flight-time)
On the other hand DC10 has approx 25% less fuel consumption and 2.4% more speed.
Maintenance costs seem to be approx. the same.
And you can probably escape one fleet change when running DC8-s into 1980-s and then change them to 767-s.