490 ie Vega 10 (most likely will be named 500 series), will be a 64 CU die paired to either a 2048 or 4096bit HBM2 interface (will be 512 GB/s mem throughput either way). Based on mem bandwidth alone it should be able to do about 43 MH eth, and about 400S/s zec, but some of that is going to be dependent on where the core is clocked (especially for zec mining).
Either way doubt it will be able to touch the 470/480 on perf/$
I am all down for more powerful cards but if they wont have a cheaper perf/$ ratio then they have to have some other pros
what do we suspect the power ratio to be like?
if we take for example the 7990 it's going to be pretty high and very hard to keep cooled down, probably not gonna be worth the try.