If you really need a next-gen console, but haven't managed to get a pre-order console for PlayStation 5 and Xbox Series X - there are still some guaranteed ways for you to get one. But it is going to cost you an arm and a leg (pretty much). As usual, there are plenty of scalpers buying consoles, then putting them up on Ebay.
According to the site, several auctions have led to people paying more than $1000 for a new console, and there are also way more expensive alternatives from greedy folks trying to make a buck. Head over this way if you want to pay $6100 for an Xbox Series X or perhaps settle for a dirt cheap one costing only $5000 on this link.
PlayStation 5 still hasn't launched in Europe, but it is out in Japan and USA since yesterday, and as you can expect, it is also a scalpers paradise. You can buy it for $5500, or opt for the better offer of getting it for $2800 (including Demon's Souls, Spider-Man: Miles Morales and PlayStation Plus).
...or you could just wait a couple of weeks and save a few thousand bucks. That's entirely up to you.