I`ve also been waiting for this monitor for the same reasons plus it has HDR600. As EsaT say it was supposed to be out in Q1 but there still isn`t anything to say it will be Q3, realistically it will be Q4 I think.
Gigabyte announced a couple of monitors the other week, the 32" FI32U monitor ticks the refresh rate and HDMI 2.1 boxes but only has HDR400, the FV43U has HDR 1000 but at 43" is too big for me so I`ll have to wait patiently for this Viewsonic