Ted Kremenek listed in his "On the road to Swift 6" post on the forums "Expand the number of platforms where Swift is available and supported" as the first item. (https://forums.swift.org/t/on-the-road-to-swift-6/32862)

Saleem Abdulrasool, who has been working on Swift on Windows, was also recently added to the core team.

So I don't know if it's actually on the roadmap, if one exists, but official support doesn't seem impossible.

Yes! Swift 5.3 is planned to introduce official Windows support, led by Saleem Abdulrasool who has done a bunch of work on it.

https://swift.org/blog/5-3-release-process/