Rust platform support is tiered[0]. Tier 1 targets are automatically tested, tier 2 targets are automatically built, and tier 3 targets are best-effort. Windows 7 is tier 1 and Windows XP is tier 3; what they're going to do is change the tier 1 Windows build to 10, but the Windows XP support isn't going anywhere.
[0]: https://doc.rust-lang.org/nightly/rustc/platform-support.htm...