Id wait and see; You could pick up an 1160 which will likely perform better than the 1070 and have up to date hardware for upcoming games.
For me, I think it’s always better to buy at the upper end; you get a better gaming experience with greater longevity, especially if you’re at 1440p rather than UW/4K. My 980 is still serving me very well, I dropped down from SLI and don’t miss it, if I’d gotten the ti I’d probably wait another generation.
As it stands I’m waiting for the 1180ti, and that’s because of want, not need. I’m waiting for the ti because I should be able to skip the next generation and continue to have a great gaming experience into the one after that. At the lower end it takes far less time before you’re turning settings right down to get decent frames.
Just my tuppence, but I suppose I’m lucky because what I spend money on is up to me; the mrs and I don’t tend to influence each others purchasing decisions. I appreciate that’s not the case for a lot of couples.