The promised 4K 144Hz G-SYNC HDR displays from both Acer and ASUS got delayed from late 2017 to 2018, and it's unknown why these 27-inch panels are yet to hit the market. Over at the Game Developer's Conference (GDC), NVIDIA told AnandTech that these displays are expected in April:
At GDC, NVIDIA has said that G-Sync HDR-supporting displays will finally ship in Q1, but noted that by Q1 it means its fiscal quarter, not calendar quarter. NVIDIA’s Q1 FY2019 (2019 because NV's fiscal year is one year ahead) ends on April 29, 2018, so it is logical to assume that the monitors will ship next month. What remains to be seen is the pricing as well as the final set of features and technologies.
Both the Acer Predator X27 and the ASUS ROG Swift PG27UQ are based on the AU Optronics M270QAN02.2 AHVA panel. The screens offer a 3840 x 2160 pixels resolution, 144Hz refresh rate, 1000 nits brightness, direct-LED backlight with 384 zones, HDR10, and DCI-P3 color gamut.