The new XPS 15 is almost upon us, but there will be no long wait for a 4K OLED option. Dell will bring the 4K OLED model to market on June 27, with the XPS 15 7590 being the first in the series to feature such display technology.
https://www.notebookcheck.net/Dell-to-release-the-4K-OLED-version-of-the-XPS-15-7590-on-June-27.425058.0.html