From Playstation Blog:

https://blog.us.playstation.com/2020/03/10/hermen-hulst-qa-interview-with-head-of-playstations-worldwide-studios/

Looks like a special case - and not all PS exclusives are coming day 1 to PC in the future.  Here's an excerpt from the interview:

PSB: Speaking of experimentation, there have been rumors of a Horizon Zero Dawn complete edition that might be coming to PC… can you confirm or deny that?
HH: Yes, I can confirm that Horizon Zero Dawn is coming to PC this summer…. There will be more information coming from Guerrilla, from the new studio directors [Michiel van der Leeuw, JB van Beek, and Angie Smets] pretty soon.

PSB: PlayStation is no stranger to publishing titles on the PC, but Horizon: Zero Dawn is one of the largest games to make that leap. Is there anything you would say to PlayStation fans? What does it mean for the future?
HH: Sure. I think it’s important that we stay open to new ideas of how to introduce more people to PlayStation, and show people maybe what they’ve been missing out on.

And to maybe put a few minds at ease, releasing one first-party AAA title to PC doesn’t necessarily mean that every game now will come to PC. In my mind, Horizon Zero Dawn was just a great fit in this particular instance. We don’t have plans for day and date [PC releases], and we remain 100% committed to dedicated hardware.