No, i've already played through more than half the campaign, and no obious hints as to if the Kryyn even exist{in the storyline, anyway}. Maybe the Kryyn were in the story from the beggining, being hinted at in very discreet and vague ways...
Possibly I've played through quite a bit of the campaign up to the mission involving Drengi itself but I've not heard of them yet. You're right though maybe they have always been in the background..
"We know now that in the early years of the
twentythird century this world
(the whole galaxy in fact)was being watched closely by intelligences greater than man's
yup and even greater than the Thalans, and yet as mortal as his own. We know now that as human beings busied themselves about their various concerns
Like the Drengin and Dread Lords for instance they were scrutinized and studied, perhaps almost as narrowly as a man with a microscope might scrutinize the transient creatures that swarm and multiply in a drop of water."