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/$