I don't know why Sony couldn't just let PS5 owners use their PS4 controllers. They are LITERALLY the same. The only difference between them is the adaptive triggers and haptic feedback. The buttons and the placements of them are the exact same. You can even turn off the adaptive triggers and haptic feedback which essentially turns the PS5 controller into a fancy PS4 controller. And because of that the DualSense should be compactible with the PS4, like there is no reason why it can't. Even the PS3 can use the DualSense.