Firstly, DualShock 4 - a.k.a. the PS4 controller - can't be used on any upcoming PS5 games, with Sony stating that it wants the new titles "take advantage of the new capabilities and features we’re bringing to the platform, including the features of DualSense wireless controller."
However, the new post on the PlayStation Blog does confirm that DualShock 4 will still be able to run on the new console when playing PS4 games via PS5 backwards compatibility, in addition to third-party gamepad controllers for the PS4.
In addition, Sony has clarified that "specialty peripherals, such as officially licensed racing wheels, arcade sticks, and flight sticks, will work with PS5 games and supported PS4 games", alongside PlayStation's Platinum and Gold Wireless headsets, third party headsets that connect via USB or audio jack, and PS Move and PS VR controllers with "supported PS VR games on PS5."
Finally, your old PlayStation Camera will also be forward compatible on PS5, for both existing PS4 games and new PS5 games that support the device, but will require the use of an "additional adaptor" that Sony promises will come at no extra cost to the user.
The end of the post promises that more "updates on PlayStation 5" are coming soon, so be sure to stay tuned to GamesRadar for the latest as it arrives. Check out the latest information on where to buy PS5.