Back in SIGGRAPH 2016, NVIDIA announced that they would take control of Mental Ray’s licensing and development. The new product was in beta at the time, boasting a new global illumination solver that was 4x faster on CPUs than the previous method, and 25.9x faster when you add a pair of Quadro M6000s into the mix. Access to the beta was free until it launched, which happened in Autumn 2016.
We’re now in Autumn 2017, and NVIDIA is discontinuing the product.
NVIDIA is not leaving the rendering market, though. The graphics vendor has several products in that space, including the very-similar Iray. In fact, it was kind-of odd to see NVIDIA maintain both products with some weird cross-overs, like how they’re bundled on 3D Studio Max for the same price as either product purchased individually in Maya. They also maintain the OptiX and IndeX APIs, which is used all over the place, even for non-graphics workloads. (VRWorks Audio, for instance, uses OptiX to ray-trace video game audio for environmental effects, which is a fairly good model of high-frequency sounds.)
Current users of the Mental Ray plug-in, or those who purchase a license before the 20th of November, will receive “maintenance releases” through 2018 (presumably while they plan their transition elsewhere). These updates will be “bug fix” updates, although NVIDIA does state that one of them will introduce compatibility for Volta-based GPUs.
If you already own a license to Mental Ray, and you will need it for longer than the time left on your subscription, then you will need to contact NVIDIA for an extension. They’re not going to just throw you out if your license expires in December, but you have obligations through February (or something).