In my experience they've tended to talk to whoever is physically closest to them, which is sometimes quite annoying. Though I've still got to (generally) choose the reactions, so ymmv; and I suspect that's likely to have been significantly overhauled in the actual released game.
In that case, I hope you are right.
If every party member can talk with NPC and make decisions that will change the world, then there is no leader, no main hero and immersion with role playing experience are gone.
I hate when games doing this...
