In a recent interview with Eurogamer, series producer Yoshinori Kitase has expressed interest in returning the core Final Fantasy series to the Windows platform. Beyond the MMOs, XI and XIV, a new game in the series has not been published to the Windows desktop OS since Final Fantasy VIII. It's clear, though, that the company maintains some interest in the platform with releases from other series like Deus Ex and Tomb Raider, not to mention the recent re-releases of Final Fantasy VII and VIII to Windows last year.
While no games from the Final Fantasy XIII series were released for the platform, Kitase reminds Eurogamer that the original XIII development took place in a Windows environment, so the notion of a release was not restricted by the development itself but instead Squenix' own market analysis and concerns about DRM. Kitase stops well short of promising a release of Final Fantasy XV via Steam, but it's clear from his words that the interest is there and that a release could easily be in the cards if the numbers look to work in the company's favor.
Source:
Eurogamer