That would be pretty dumb. Everyone that follows gaming knows this is THE Xbox show to watch. A random UI show off or controller show off or whatever small thing will only make it so PS themselves gets less coverage. An announcement of their August show would also not accomplish much. It's an announcement so people are gonna be like "Oh, ok cool I'll watch it in August" and keep their eyes on the Xbox show.
The only thing that could even potentially "counter" MS's conference is if they were to do their big August show on the same day as the Xbox show (and at that point they'd have to announce it like...... today) which probably just ends up being detrimental to both companies as both companies gets fewer clicks and nobody's happy.
I guess something that'd actually get eyes off MS show without hurting themselves would be opening preorders. But that'd be just a shitty move to do.