No it wasn't. The extra Duran mission focused on the return of the hybrid in the near future. Now this is happening and the teenage kids are whinning about it.
The hint really did not say anything about anything. We knew Hybrids existed (we knew nothing about what they looked like, how powerful they are, how many their are, etc) and that Duran served some greater master (almost everyone assumed this was Xel'Naga). That's about it.
I always thought of them coming in the same way Tierdal seems to have conceived it: as working within the already established system. A fourth faction with their own political and social intrigue that would form alliances and wage war based on their goals.
They do indeed fit this description at the most basic level, except that they are portrayed as essentially super beings whose only goal is to destroy. They are working outside the established system and Amon is literally seen as a god for some (Tal Darim). Its kind of hard to work a god into political systems.
For example, instead of having characters be motivated by political/power reasons, we have to just accept the fact that Kerrigan can't be killed because of a prophecy and a vision that the universe will end if she dies. It's nearly impossible to have characters navigate political complexities when there is a giant trump card like that.