I personally think it will either come down to a as EvilVik says.. a) person wishes the power of the tadpole (and if reputation with tav = neutral to low) = turning hostile and/or joins absolute or b) people with low approval getting taken over by the will of the absolute, sort of like the absolute tries to do until shadowheart uses the artifact to block her/it out.
We will have to see. I doubt the characters will just die out by default, but I assume some sort of loyalty check could be programmed in. Some characters are very hard to please of you are good aligned anyway. Such as Astarion and Lae'zel lol. I never seem to end up with her higher than medium approval . doesn't mean I turn her back on her all the time though as her turning you down dialogue suggests xD.
I just dont have a Gith worldview
Personally I think it will just come down to everyone not in the party at some point being outside of the sphere of effect of that artifact, and then being Absoluted up because of it.
...I should probably try a run without Shadowheart in the party just to see what happens in that scene when she isn't in it.
. doesn't mean I turn her back on her all the time though as her turning you down dialogue suggests xD.