When I first made that post, I did think about including the percentage, but it would have been something like 5% everywhere, which might be more demoralizing than anything else really!
We are supposed to reach an important milestone next month, so I'll make an update then. It's also tricky to think of a percentage when we are not sure of the level of polish we want the game to have (will we put in more talking animations? more background animations? more dialog branching? one or two additional cutscenes?).
As for a demo, I don't know yet, but if we ever finish the game, there sure will be trailers... but let's not get ahead of ourselves!