The AMD Ryzen release date may have been revealed by the Game Developer Conference 2017 schedule. According to it, Ryzen will be out by March 3.
A description of an AMD talk on Ryzen CPU optimisations tells would be attendees to “join AMD Game Engineering team members for an introduction to the recently-launched AMD Ryzen CPU”.
Why March 3? Well, GDC 2017 runs from February 27 to March 3. This would put Ryzen’s outermost release date being March 3.