In January 2019 Dell announced that it will release 15" OLED models of its 2019 XPS 15, Dell G7 15 and the Alienware m15. Back then Dell said that the laptops will ship in March 2019, but Dell’s VP General Manager now says that the target date is April.
We've been waiting for OLED laptops for many years, so one more month to wait is not a big deal - if indeed the OLED laptops will ship in April. In January Samsung Display announced that it will start mass producing its new 15.6" UHD (3840x2160) OLED display panels in February 2019. Perhaps Samsung is delaying its mass production - or perhaps this is Dell's decision or need to postpone.