There's not much to go on at the moment - though it doesn't look like we won't have to wait long to find out more as the website suggests May 2019 is a date to get excited about.
It is possible to glean a few things from the website though. The image of the new headset - known as the Valve Index - shows the underside which includes an IPD slider (for adjusting lens positioning) similar to that on the Oculus Rift.
This official mysterious reveal nearly confirms the leaks we saw last November where multiple images of the headset were posted on Imgur. Those images were, of course, unverified at the time, but now appear to be genuine and show a design that gives a few things away.
Built-in headphones, front-facing cameras and what appears to be a padded headband are all present. At the time of the leak, UploadVR suggested the new headset is also built with a 135-degree field of view - much wider than the current standard. The lenses are also apparently capable of a resolution similar to the HTC Vive Pro (around 2800 x 1600).
There's no official mention of the accompanying controllers, but we wouldn't be surprised to see Valve's long-rumoured, much talked about Knuckles VR controllers making an appearance in May too.
Interesting to see Valve making a departure from the partnering HTC. We wonder if this is down to the fact that HTC has been pushing more and more towards the business market with the recent updates to the HTC Vive Pro and other headsets. Perhaps the Valve Index is going to be much more consumer-focussed. Only time will tell.