Sony has confirmed in a Blog Post that all the trophies you have earned from PS3 and PS4 will stay on your account and come with you to PS5.
This news was found at the bottom of the blog post, which highlighted a bunch of changes coming to the trophies system this week and will carry forward onto the PS5, including new trophy level icons, and a revamped level and calculation system. This was expected as PS3 to PS4 did the same thing, but it is still nice to get an official confirmation from Sony. But, some PS5 games might have a separate trophy list, allowing you to them twice if you already have the Platinum.
This news came as Sony revealed a teardown of the PS5, detailing the internal hardware in a lot of detail.
The PS5 releases on November 12, 2020, in the US and November 19, 2020, in the UK and EU.
Source – [PlayStation Blog]