As we all know, there is some sort of relationship going on between the Oculus developers and Valve. When Half Life 3 came to question, one fan went to Oculus to get an answer.
For a team that behaves unethically, Oculus gave a pretty much formal answer. The team revealed that Half Life 3 on the Oculus Rift is neither a confirmed thing nor something false entirely. As such, the idea of Half Life 3 being played on the VR headset could be in the works and is subject to confirmation.
Fans are certainly hoping for the positives to take place. The immersion of the Rift with Half Life 3 will definitely be the greatest thing that can happen to the gaming industry.
On the other hand, it could be Oculus simply saying that they have no clue about it. As such, it is best to take this with a teaspoon of salt. The only way this can be confirmed is with time. Of course, the duration of it is unknown.
