not quite double the performance but it can almost twice as fast depending on games. going from 980ti to 1080ti is almost double the performance (look at 4k performance where CPU bottleneck is much less of a concern):
but you will not going to get it right away after new generation of GPU comes out. GPU maker are holding back the performance increase at least in two steps so they can maximize their profit. right now nvidia still at least offering 30% performance increase every year (at least you can expect that). on AMD side maybe you can get that 30% increase after two years.
not quite double the performance but it can almost twice as fast depending on games. going from 980ti to 1080ti is almost double the performance (look at 4k performance where CPU bottleneck is much less of a concern):
but you will not going to get it right away after new generation of GPU comes out. GPU maker are holding back the performance increase at least in two steps so they can maximize their profit. right now nvidia still at least offering 30% performance increase every year (at least you can expect that). on AMD side maybe you can get that 30% increase after two years.