I'd say wait. I wouldn't get an <8GB GPU for over $300 currently. There was some info about a 2060ti a few months ago. That might add 8GB instead of 6GB. We cannot really talk about GPUs today being good enough for next gen 4K games until we see them.
There's not going to be a 2060 Ti, you may be confusing with the 1660 Ti, which is rumored to come out by the end of next week, won't support raytracing and will be weaker than the RTX 2060.
The RTX 2070 specs are not far from the 2060, the 2060 even uses the same TU106 core as the 2070, but with parts of it disabled, I don't think there would be room for a 2060 Ti.
Is it worth it to upgrade from a 970 to a 2060? Or should I wait a bit.
The current and nearby future options that would perform better than a 970:
- GTX 1660, rumored to come out next month, 6GB of GDDR5 memory, rumored MSRP is $240, I'm speculating that it'll be around 10%-ish better than the GTX 1060/GTX 980, not worth upgrading from a 970 to this unless you really need a cheaper upgrade.
- GTX 1660 Ti, rumored to come out by the end of next week, 6GB of GDDR6 memory, rumored MSRP is $280, I'm speculating that it'll have close to GTX 1070/GTX 980 Ti performance, would be a decent upgrade, but not enough for 4K (and when it comes to the most demanding games, it's likely not going to be enough for 1440p either).
- RTX 2060, 6GB of GDDR6 memory, $350 MSRP, has around GTX 1070 Ti performance.
- RTX 2070, 8GB of GDDR6 memory, $500 MSRP, is slightly better than the GTX 1080.