Duran's Fate...

I am sorry for those who preferred to let the mystery but Duran is the Hybrid who was rumored being the Overmind all along.
Duran is killed by prelate Zeratul when the Dark Templar and his companions searched the Dark Moon planet in hope of regrouping with Artanis and the survivors of the Khalai.

It seems weird but Duran was not even terran or zerg or protoss but in "secret origins" the UED turncoat has laready set many hybrids on many worlds so it is clear there is a good opening for a sequel.