The Dell XPS 13 9390 does not exist. Here's why
Dell just announced a refresh of nearly its entire Inspiron family this week all coming with Intel's 10th gen Comet Lake-U processors. Not to be left out in the dark, the current XPS 13 9380 with Intel Whiskey Lake-U will also be updated to Comet Lake-U for a launch this September. One would reasonably assume that the Comet Lake-U-powered XPS 13 will be the XPS 13 9390 similar to the XPS 13 9380, 9370, 9360, and 9350 models that precede it.
In a curve ball from Dell, the "XPS 13 9390" will officially be called the XPS 13 7390 instead. The change follows on the footsteps of the new XPS 15 7590 which many had presumed would be called the "XPS 15 9580" to succeed the XPS 15 9570. The new naming convention will bring the XPS series more in line with the existing naming conventions of the Inspiron and Latitude series.
As an example, the Inspiron family consists of the entry-level Inspiron 3000, mid-range Inspiron 5000, and higher-end Inspiron 7000. An Inspiron 9000 does not exist and so Dell will be dropping the "9000" naming that was previously exclusive to the XPS family.
Fortunately, all four digits still tell you exactly what you need to know about the model. The first digit tells you the class (3 - entry-level; 5 - mid-range; 7 - high-end), the second digit tells you the screen size (3 - 13-inch; 5 - 15-inch; 7 - 17-inch), and the last two digits tell you the iteration (90 will be newer than 80, 70, etc.).