If you were expecting Destiny 2 to run at 60fps on your shiny new PS4 Pro, I'm sorry to say that you'll be disappointed.
Bungie has revealed that Destiny 2 will run at 30FPS on all consoles, even the powered up ones. Here is what Luke Smith had to say when asked for a reason:
The console, the PS4 Pro is super powerful, but it couldn't run our game at 60. Our game's this rich physics simulation where collision of players, networking, etc, and like, it wouldn't run.