Here are first several high ISO sample images of new announced Nikon D500 (Amazon, B&H Photo Video, Adorama). These sample images are taken from ISO 25,600 to ISO 1,640,000, but only on D500 LCD screen.
ISO Test
High ISO Comparison: 5Ds R Vs. Nikon D810 Vs. 5D Mark III Vs. 7D Mark II by Imaging Resource
Imaging Resource has posted their first review of Canon EOS 5Ds R full frame DSLR camera. 5Ds and 5Ds R will be shipping in late June, 2015, and will be able to pre-order online tomorrow night, Monday, March 23, 2015.
High ISO Comparison: Nikon Df Vs. D800 Vs. A7R Vs. 5D Mark III
Here are high ISO comparison of Nikon Df and Nikon D800, Sony A7R, Canon EOS 5D Mark III.
High ISO Comparison: Olympus E-M1 Vs. E-M5 Vs. Panasonic GX7 Vs. D7100

Here is the high ISO RAW and JPEG files comparison of new announced Olympus OM-D E-M1 and E-M5, Panasonic GX7, Nikon D7100.
High ISO Comparison: Canon EOS 70D Vs. 60D Vs. 7D Vs. Nikon D7100

dpreview has updated some more sample images of Canon EOS 70D. And here are several pictures of high ISO comparison for new announced Canon EOS 70D and 60D, 7D, Nikon D7100.
Nikon D7100 High ISO Test
Nikon D7100 high ISO test from ephotozine now available. You can click the image to see original size. The ISO test is from ISO 100 to ISO 25600.
