Using an i7-4790K, GTX 980 ti, 16 GB RAM, and an SSD, it will load into the main menu in about 5 seconds (hitting ESC through the intro vids). I will then load from the main menu into an actual savegame file in around 8 seconds (hitting SPACE to skip the storybook dialogue).
We know the specs of the PS5, so the above should be a good baseline for comparison.
That's fast CPU, fast RAM, and fast SSD. Just be aware that a console's OS will likely not function 1:1 with a PC OS. Very often, consoles will also have security checks, the inability to skip logos, etc.
All in all, I'd say the PS5 should be pretty fast at loading the game. I'm going to estimate around 15 seconds from main menu to in-game, tops, as long as one can skip through the vids.