According to the latest round of rumors, Nvidia is currently working hard on a new mid-range GPU, probably known as the GeForce GTX 950 or 950 Ti, to compete in the sub $150 market with AMD's Radeon R9 370.
This new graphics card from Nvidia will reportedly feature a "GM206-250" GPU, which will be a cut-down version of the full-sized "GM206-300" GPU used on the GeForce GTX 960. The GTX 960 comes with 1024 CUDA cores and features a price tag of $199, so a cut down version of this card will almost certainly pack fewer CUDA cores and a lower price point.
It's expected that the GeForce GTX 950 Ti would replace the existing GTX 750 Ti, a first-generation Maxwell card, in Nvidia's current product stack. Considering the 750 Ti currently retails for $149, it would make sense for Nvidia to launch a new product with better performance at the same price point to compete strongly with the $150 R9 370.
Not much is known about the 950 Ti at this stage, so it's hard to make any assumptions about how the card will perform relative to other cards currently on the market. Considering Nvidia just launched the GTX 980 Ti and the Titan X shortly before that, the 950 Ti isn't going to hit the market any time soon.