Word is hitting the web that NVIDIA's next-gen GP100 based flagship may arrive as soon as April. TweakTown claims the GeForce GTX Titan will get a HBM2-based successor with 1TB/s of memory bandwidth.
Around Computex in June, NVIDIA is expected to reveal its GP104-based models, these cards will replace the current GeForce GTX 980 series. According to the rumors, the GTX 1080 (or whatever it's called) lineup will use GDDR5X memory with a bandwidth of 448GB/s.
There's still some uncertainty about the GeForce GTX 980 Ti successor, this card will be based on the GP100 GPU and reportedly uses HBM2 memory. An exact launch date is unknown, TT speculates it could be sometime later this year, depending on AMD's enthusiast lineup:
Then we have the elusive GeForce GTX 980 Ti successor, which will also be powered by HBM2. I think this card will most likely arrive sometime later in the year, depending on AMD's movement in the enthusiast GPU sector. The Titan X successor will be incredibly fast (I would say 1.5-1.8x the Titan X) and so will the GDDR5X-powered GTX 980 successor (again, most likely 1.5x the GTX 980). These two cards will fill the most important parts of the market, while keeping its secret weapon (the GTX 980 Ti successor) waiting in the darkness.
Later this year we can also expect the GP106 and GP107 based mainstream cards.