https://www.pcgamer.com/valves-vr-headset-is-called-index-and-its-coming-soon/

Without any sort of announcement, a teaser for the Valve Index has appeared on Steam. It is clearly Valve's VR headset.

The only text in the teaser reads "Upgrade your experience" and "May 2019," so presumably that's when the Index will go on sale, given that the word "sale" is in the URL.