With smaller manufacturing technology, the big benefit to amd and nvidia is lower cost of production.
So long as there is not a price war, you can expect the new cards to sell at about the same price/performance ratio as now or a bit better.
If you have a need now for a graphics card, buy what you need now. If you wait for the next best thing, you will wait forever.
Today, a R9-390X will give you very good gaming at 1080P.
Similarly a GTX970 will do the same requiring much less power and cooling.
Keep such a card until you need more. Perhaps for 1440P gaming or a 4k monitor.
Then just sell it and buy what you newly need.
For fast action shooter games, the graphics card is all important.
For strategy games, sims, and mmo types, the individual cpu core speeds are all important; they depend on the single master thread for performance.