It is worth the upgrade if you want the increase in performance, which would be about three times what you have on that RX 570, based on a GTX 1080. I probably would recommend NOT going that route though, since you'd have to buy a used or refurbished card to do that. I'd look at the RTX 2060 or 2070, which will probably be seeing reductions in price fairly soon when the "Super" models are released. Or wait to see what Navi brings from AMD.
I cannot recommend buying used cards in this day and age when most of them are a real gamble as to whether they were used for mining or have already been overclocked to death and that is why they are being sold. I wouldn't buy a used graphics card from anybody I didn't know well enough that they...