It's specification has announced, we can roughly estimate its performance.
It has same memory bandwith and 26% more CUDA cores compared to 1070.
Maybe benchmark will show about 31Mh/s on ethereum and 600sol/s on Zcash.
It won't outperform a GTX 1080 on Zcash - I'd guess more like 480-500 sol/s ballpark at optimal "full hash" settings.
A hair fewer cores than the 1080, and the memory system isn't a big factor to Equihash algorithm.
It SHOULD outperform the 1070 and 1080 on ETH, and I won't be shocked if it gets into the mid-30s like a 1080ti - but I suspect memory system will limit it to only a little better than the 1070.
I'm putting one on pre-order later today to check it out - worst case it should fall into the same hash/$ ballpark as the other high-range NVidia Pascal cards on ZEC.