I would wait for 2070. By then we should have neural implants that allow us to use our brain's capabilities for powering games and not even need a GPU card at all.
Yes, that is a joke.
Honestly though, it's pretty hard to answer your question without some kind of outline regarding your expectations, games, resolution, settings, number of monitors and whether you are multi-tasking with streaming or encoding apps simultaneously. At this point I don't think I'd recommend that anybody buy a 1070, unless you come across a great deal on one or truly need it now when prices on both the 2070 and the 1070 are likely to be lower once that gen of cards hits the market. So regardless of WHICH card you end up going with, prices are likely to be significantly lower after the release of the newer gen because there will be more overall supply in the market.