In an interview with Ascii, FFXVI producer Naoki Yoshida revealed that production on a PC port will start after the PS5 version launches. There is no concrete window for when to expect it, but he stated that development will be slow and steady. [Thanks, Ascii!]
Rumors appeared in early 2023 about a PC release of FFXVI. This was due to a 2020 trailer showing that the game would come out on PC, and then a 2022 trailer talking about the 6-month PS5 exclusivity period. We took these two pieces of information to mean that the PC version of the game would come out after six months. In January 2023, Yoshida specified that the team is only focusing on the PS5 and warned against expecting the game on other platforms. Though he did not give a specific time frame for when development will start, it looks like PC players can expect to explore Valisthea some time in the distant future based on the interview.
Here is exactly what Yoshida said in the Ascii interview:
In regards to the development of the PC port, we plan to slowly work on it after release [of FFXVI for the PS5].
Final Fantasy XVI will be the latest entry in the long-running Final Fantasy JRPG series. Like FFXV, it will be closer to an action RPG than the traditional turn-based combat. However, it will still have recurring motifs such as Chocobos, summonable monsters (Eikons), and crystals.
Final Fantasy XVI will come out on the PS5 on June 22, 2023. A PC port of FFXVI will be in development some time after that date. Yoshida also states that the team wants the game to fully satisfy players on its own, and does not plan on releasing DLC unless fans ask for it.