You're playing games now, and want
The 970 was on par with the 780 ti and cost £240
1070 was on par with the 980 ti and cost £380
2070(s) on par with the 1080 ti and cost £475.
If you're at that stage where you notice your card doesn't keep up, why wait in hope that something, which doesn't even exist yet....we literally have zero idea of date/performance/price, or even naming.
Basing your decisions on speculation, and not fact, and the fact is your card is no longer performing how you hope.
One thing I don't regret about being a pc gamer is that I base my purchases on what I can physically buy. I've seen people regret not buying things sooner, but I've never seen anyone with buyers remorse like 9 months later, as they've enjoyed their tech in the meantime and not spent the time worrying about what come in the future.