Khronos Group just posted an announcement on Khronos.org, "The Vulkan specification is complete and undergoing legal review and final polishing. The Vulkan conformance tests are being finalized and multiple member companies are preparing drivers for release. Implementation feedback is the vital final stage of making any Khronos specification ready for primetime, and the Vulkan 1.0 specification will be published when the first conformant implementations are confirmed."
From a source involved in Vulkan's development, I received some additional information. The source that can be trusted reported, "I can confirm that the spec was finished a couple of weeks ago and is now going through the (longish) Khronos legal review process. I'm not allowed to talk about when it might go public, but I will say that the gating factor for release will be availability of product-quality implementations. That's a pretty high bar, given that the API has changed a lot since GDC and, well, end of year holidays are hell on engineering schedules. Still, it won't be *very* long..."