Today AMD is anticipated to introduce the Radeon RX 5500 XT, which also has 1408 shaders. This model has a 1.7GHz clockspeed and a 128-bit memory bus with 4GB to 8GB of GDDR6 memory. Igor's Lab claims the Radeon RX 5500 XT will not be able to beat the GeForce GTX 1660 SUPER, but the latter will be significantly slower than a possible future Radeon RX 5600 XT.
Igor's Lab crunched some numbers and came up with the following performance chart. The values of the Radeon RX 5500 XT, GeForce GTX 1660 SUPER and Radeon RX 5600 XT (which is still rumored) are all extrapolated, so take them with a grain of salt. The chart reveals that after the introduction of the GeForce GTX 1660 SUPER, the GeForce GTX 1660 Ti may not make a lot of sense anymore. The Ti is a tad faster but the SUPER will have a better price/performance ratio.