For what it's worth
the initial DR2 announcement was even lighter on details, only having the setting, counterargument mechanic, and art (no names) for Hajime, Chiaki, Akane, and Togami. (Apparently a lot of the early DR2 material suggests Akane was going to have a larger role in the game...?)
Of course with how the franchise has grown since then I'd be very surprised if they didn't announce alongside a fairly fancy trailer, but they seem to know not to spoil too much. Alternatively you could look to DR:AE's
final trailer to get a feel for how much they feel like revealing, but I imagine they felt a little freer with AE since it wasn't a murder mystery.