I'm pretty sure that there will at least be full dialogue for main quest sections.
There better be...
That sounds like a threat although it isn't. I don't plan on raiding Larian Studios again, it'll simply be a shame if Original Sin was nearly absent of all the well-written PC dialogue Larian excels at. Based on that teleportor scenario I guess we'll have full PC dialogue in side quests and encounters too. For irrelevant townsfolk I think keywords work just fine, most interactions with unimportant folk in RPG's is normally always simply questions which could be presented as keywords without any problem.
