I'm not expecting that we will get any more content at all throughout the EA; we will have this, Act 1, and that is all. That's what they're told us, I'm fairly sure (I don't have a quote, sorry), and it would be a bad idea for them to backtrack on that and show us more game, rather than spending their time and effort getting all of the issues that are currently problems, sorted out. We're not here to 'play the game early'; we're here to test and the give feedback, and generally to help them with our time and data, for free, because we want the game to be polished when it does come out in full.
I would absolutely support a roadmap, and more active communication form Larian about all aspects of this EA; both are fundamental to helping us help them.
