Update: nVidia may release THREE new GPUs in June instead of two, with the 1080 Ti rumoured to release alongside the other two.
The latest in nVidia’s graphics card lineup will feature their new Pascal architecture, which promises enhanced power efficiency and floating point performance. Based on a GP104 core, the GTX 1080 will be nVidia’s flagship card and may use 8GB of GDDR5X  memory to achieve what is speculated to be as much as 384GB/s depending on memory clock over a 256-bit bus, which should eliminate bottlenecks and enable smoother high resolution gaming, plus post-120Hz refresh rates for high-end VR.
There is doubt whether nVidia may actually be able to equip a GPU for release in June considering JEDEC only finalised the GDDR5X standard in Q4 2015, but hope remains.
The card will be manufactured on nVidia’s 16nm FinFET node and likely feature 2048 CUDA cores for a theoretical performance of 6.2TFLOPs (single precision), though this is just our own speculation based on existing information, it may differ based on the GP104 core.
The GTX 1070 will use ordinary GDDR5 memory and a similar core count to the current 980/970 lineup at 1664 CUDA cores, with the same 256-bit bus.
These cards are going to release in June.
Sources:  http://www.bitsandchips.it/9-hardware/6854-nvidia-gp104-con-due-pcb-reference-base-gddr5-e-premium-gddr5x