https://www.pcgamer.com/nvidias-benchmarks-claim-the-rtx-2080-will-be-50-faster-than-gtx-1080/

There's been a lot of discussion about Nvidia's new GeForce RTX cards. With the big focus on ray tracing, many have expressed concern that the Turing architecture won't be much faster in existing games—or if you prefer, faster when doing traditional rasterization. Nvidia briefed members of the press on a lot of additional details regarding the Turing architecture and changes, and we'll have full performance benchmarks when the cards actually launch, but Nvidia provided the following slides to give a taste of what sort of performance we can expect:

Starting with a comparison of Turing against Pascal, the most pertinent numbers are the dark green bars. On average, Nvidia expects the RTX 2080 to be around 50 percent faster than the GTX 1080. We can't say right now how accurate that number is, but Nvidia did reiterate the "50 percent faster per core" message, and that's without using the new features.