A 4K Chromebook has shown up on the Chromium OS gerrit, suggesting that a Chromebook with a 4K display is currently being developed and may arrive on the market for interested consumers sometime in the future. According to the Chromium gerrit the 4K Chromebook is being referred to as 'Atlas' as that seems to be the codename for the device being used internally, and the exact display resolution listed is 3,840 x 2,160. Right now the highest resolution on a Chromebook doesn't stretch beyond 2K, so this would be a significant step up in terms of screen resolution for Google's popular Chrome OS laptops.
First spotted by user nbsp on Reddit the screen resolution and the codename for the Chromebook are the only major details about the device that are known at this point in time, which means there's no information about other hardware specifications, a potential release date, or a cost, though, considering the resolution of this Chromebook would be 4K it's not likely that it would be lumped in with some of the budget models that can be picked up for under $250, which is something to remember if the thought of a 4K Chromebook excites you.
Major details aside, Atlas is also listed as lacking an SD card slot, a feature which many Chromebooks have. This means that it would likely rely on internal storage and cloud storage only. This may also point to the device coming with a potentially larger internal storage amount to supplement the lack of expandable storage. If a 4K Chromebook is in the works there are other unknowns besides the price point, when it will launch, and what specs besides the display resolution the Chromebook will carry, such as who will be manufacturing the device. That said, it's not impossible that it would come from a brand that has already manufactured a Chromebook for the high-end side of the market, such as Google or Samsung.