The high-end Turing GPUs do not seem to be a great upgrade choice for the time being, but what about the upper-mid-range RTX 2070 model? According to the latest leaked Time Spy results, the RTX 2070 GPU is indeed faster than the GTX 1080, however, the tested sample was already factory-overclocked, so the actual performance difference between a stock RTX 2070 and a stock GTX 1080 might be negligible.
https://www.notebookcheck.net/Nvidia-s-RTX-2070-slightly-faster-than-the-GTX-1080-in-latest-leaked-3DMark-Time-Spy-test.338054.0.html