At the moment, no not really. It's a new standard and will take some time for developers to use as their default. This assumes of course they don't just skip it like they have with previous DX versions or that they will actually implement the features in DX12 that make it better than DX11. When done right performance does increase. AMD seems to get a bigger boost but Nvidia cards are father ahead to begin with so it does not make the AMD cards better than Nvida cards.
As for prices, supplies seem to keep being low so they keep selling above MSRP. Frankly do not expect them to dip under MSRP with any regularity until after the next gen comes out a year from now. Even then the prices won't dip that much judging by the price drop in...