They aren't going to announce that during the conference. It's not worth their time.
Probably depends on how many they have coming. Would be very easy to include a slide with a dozen titles on it and say something along the lines of, "Since we launched PS2 Classics on PS4, over _____ million games have been downloaded by PlayStation fans across the globe."
Makes even more sense if the next line is, "We've heard you, and today, we're pleased to announce that PS1 Classics will be coming to the PS4, with X, Y, and Z available for download at the conclusion of tonight's briefing."