According to Valve, Half-Life 3 game won't be a virtual reality (VR) game as it will not have a support for any VR headset, including Valve's own HTC-made Vive VR headset.
At a panel that was dedicated to the future of VR, Valve's Chet Faliszek was not surprised by the question from the audience and said that VR was not going to be a part of Half-Life 3.
He also added that VR still has and will have plenty of problems including a bunch of cables. While currently every VR peripheral needs a wired connection in order to do high-data low-latency stream, wireless is definitely the future, but it will be quite hard to do.
Although the idea of playing Half-Life 3 in VR sounds amazing, it appears that it is still early for VR gaming on such level, at least if you ask Valve. Valve's Vive VR headset is still on schedule to be released in 2016 with limited quantities expected to ship this year.