Sangsu Kim writes:
The first pre-4.0 XFree86 snapshot is now available. It is
labeled as version 3.9.15. See our snapshots page for further
details. These snapshot releases are work-in-progress snapshots of
the XFree86 4.0 development code. If you’re looking for a stable
version of XFree86, you will be better off with the latest 3.3.x
release in most cases.