No it isn't, they already ported the first game to PC, it's sold well over a million copies, they continued to port more games to PC, them porting the sequel eventually is a very reasonable assumption to make.
Answer me this, when people talk about the PS6, is your honest reaction "it doesn't exist because Sony haven't said it does"?
No, but the "Only on Playstation" text was removed from the Amazon listing (which is exactly how people figured out the Horizon and Days Gone ports), it was listed in one of the GeForce Now leaks, and the port's been listed on third party sites with a February release date which would coincide with the approximate time of a rumoured State of Play.
So no, no official confirmation yet, but it shouldn't be long.