If they are only around the 1070/80 performance, then their dead in the water, as Nvidia have just about all the market, a card is needed to get them switching.
I thought Vega was going to be a "family" of GPU's though?
I was going to get a gtx1070 to replace my gtx970 until I saw the price they were released at (nearly £100 more than I paid for my 970)
If AMD release a Vega card that offers 1070 performance for a more realistic budget such as £270 (the budget i'd set myself as an upgrade) then I'd definitely be interested