It's all about when's the right time to show the game. This is a story based game, so unless they're showing Kara gameplay, a new character, or an overarching trailer, I assume they don't want to show much, or I hope so, with Beyond they showed way too much, and I hope Quantic Dream learned from that.
That being said, Beyond was shown at film events as well as E3 if memory serves, so I wouldn't be surprised if we saw Detroit before E3, but that's up to Sony, and I don't think Sony would allow it to be shown before E3 unless it's possible it's a 2017 game. I don't think QD are that big on Twitter, in general I don't think they're a studio that likes to talk about their game until they have something concrete to show.