At this point, no one should misunderstand and think some totally new tech appears. The 590 will be based upon the same tech as the RX 580, it´s a slightly tuned up version. In the best case scenario the 590 would be built on sligthly lower nm, and could in that case, use less power (which is always a small good thing).

The tests show on ONE game
  590        580   
6389 vs 5793   + 10,3% faster
3570 vs 3160   + 13,0% faster

this will give some indication of the speed. No one with a 580 should buy a 590 if the coming results are the same, but someone with an older GPU could choose 590 over 580 or 1060 if the price just is right, and that is my big  Q ?
The VEGA is a good card, but with the high prices, it´s probably not worth the money. If the 580s would drop a little and 590 would keep the 580 price, this could be a hit. But I am afraid 580 stays the same, and 590 becomes more expensive, and then, it won´t rock the market.

Doing so for 6-9%  so much  noice for nothing