As NVIDIA revealed last week, there will be no Volta gaming GPUs until sometime in 2018. NVIDIA has been keeping very tight-lipped about its next-generation gaming GPUs but they could potentially arrive as early as Q1 2018.
We still don't know whether NVIDIA plans to launch Volta gaming GPUs first, or intends to launch a Pascal refresh as some rumors indicate. Given the underwhelming performance and power efficiency metrics of AMD's Vega, NVIDIA is unlikely to rush its Volta-based GeForce GTX cards to the market.