I am seeing estimated mining performance figures of RTX 2080Ti at 69MH/s. Please see source here: https://www.bitnand.com/product-page/nvidia-geforce-rtx-2080ti-fe

Does that make sense to you? Let's compare GTX 1080Ti vs RTX 2080Ti memory performance here.

GTX 1080Ti vs RTX 2080Ti
Memory type: GDDR5X vs GDDR6
Memory speed: 11Gbps vs 14Gbps (+27%)
Size: 11GB vs 11GB (same)
Interface width: 352-bit vs 352-bit (same)
Memory bandwidth: 484GB/s vs 616GB/s (+27%)

Given ETHash is a memory intensive algorithm that does not depend much on the GPU itself, the difference in memory performance should be a good predictor of RTX 2080 series performance.