If you already own Ghost of Tsushima on PS4:

You can pre-order an upgrade to Director’s Cut on PS4 for $19.99 USD. This upgrade will become available starting on August 20.

Starting on August 20:

If you bought Director’s Cut PS4, you’ll be able to upgrade to Director’s Cut PS5 at any time for $9.99 USD You can also upgrade directly (from original Ghost of Tsushima PS4) to Director’s Cut on PS5 for $29.99 USD