This might be an opportunity for only the most dedicated PlayStation fans, but Sony will open pre-orders for the PS5 to a limited number of people - despite the fact we still don't know the price or release date of the console.
Invitations for pre-orders are being sent to some PSN users who register through the pre-order site, although those chosen are selected "based on previous interests and PlayStation activities". Those who receive an email invitation will be alerted before pre-orders begin, have a limited amount of time to place an order, and the whole process will work on a first-come-first-serve basis. You can't just buy everything, either: there are restrictions on how many items you can pre-order, with a limit of two on accessories like controllers, and only one PS5 console can be bought per PSN ID.
It's worth noting this pre-order initiative currently only ships to US addresses, so if you're based in Europe, I'm afraid you'll have to wait longer for the opportunity to place an order. Or find a reliable buddy in the US who won't steal your PS5.
Of course, given you don't have to put any money down for this initial process, it may well be worth doing if you're a die-hard fan: but the idea of signing up for the opportunity to buy a mystery price console (of unknown release date) is pretty amusing to me. I wonder if some people will be in for a surprise.