Over at the B3D forums users claim that  big Pascal has taped out, and is on TSMC 16nm and the target release date for this GPU is Q1'16. The product would be released as GP100 and will be the succesor to the GM200 series GPUs. 

A tape-out simply means that there is an initial engineering sample batch for internal testing purposes released. With the pascal architecture Nvidia as well will make a move towards HBM memory (stacked on die memory), however they will jump right towards generation v2 of HBM, meaning they could inject up-to 32GB pf memory on the GPU. 

It is estimated that ther shader processor count for big pascal is anything from 4500 towards 6000 units. Big Pascal made on TSMC's 16 nanometer silicon fab process with a release in Q1 2016. 

Time to revive this thread. My info says big Pascal has taped out, and is on TSMC 16nm (Unknown if this is FF or FF+, though I suspect it is FF+). Target release date is Q1'16. This is a change from Kepler and Maxwell where the smallest chip (GK107 and GM107 respectively) taped out first. Maybe the experience with 20nm was enough for NV to go back to their usual big die first strategy. Given the huge gains in performance compared to 28nm, and the fact that the 16nm process is both immature and quite expensive, I suspect the die size may be a bit smaller than what we've seen with GK110/GM200. 

NVIDIA Big Pascal Taped Out - GP100 Silicon