Radiant Story takes care of dead quest givers.
I hope so. The only example they've given so far (if the quest-giving shopkeeper dies his sister takes the shop and quest over, or something like that) involved a planned death of that shopkeeper, because another quest involves killing him. So I'm not so sure to what extend the game actually reacts to quest givers dying unexpectedly.
After all, switching from 1 questgiver to another if the first one dies also means that the other person needs to have their own voice acted dialogue for the quest, unless this second character is of the same race and gender as the first quest giver...