I wouldn't recommend going for the 1070 as soon as it launches.
Wait for aftermarket vendor cards, you'll get better performance, thermals and volume - they'll drop the Founders Edition first, and that's basically a reference cooler (read: weak) for a substantial price premium.
Furthermore, might also be worth waiting for the Polaris launch - AMD cards are typically a better investment than nV, and their performance grows over time - case in point, 280X vs 770 - as well as superior performance in next-gen APIs as they start to roll out (as nV's current crop of architectures are designed around DX11 (Pascal is more or less literally Maxwell ported to 16FinFET)).