PS5 pre-order date will be announced ahead of time, Sony has confirmed in conversation with Geoff Keighley.
Eric Lempel, Sony Senior Vice President of Marketing, told Keighley in a recent livestream:
I got a message from someone saying people are lining up at stores, and we had no idea why. We’ll let you know when pre-orders will happen. It’s not going to happen with a minute’s notice. We’re going to, at some point, let you know when you can pre-order PS5.
We’ll let you know when the announcement is made, and the date and time of when PS5 pre-orders will be taken.