4K displays are starting to go mobile. Acer has just added a 4K option to its Aspire V Nitro notebook family. The Black Edition system starts at $1,499.99, and it packs a 15.6" 3840x2160 panel with some pretty powerful hardware.
Inside this heavyweight are a quad-core Core i7-4710HQ processor, one of Nvidia's GeForce GTX 860M GPUs, a generous 16GB of RAM, and a 256GB solid-state drive that shares storage duties with a 1TB mechanical hard drive. Acer's announcemen't doesn't mention size and weight, but the Black Edition's 1080p siblings are all 1" thick and 6.61 lbs. I'd expect the 4K model to be in the same ballpark.
Even the lure of a 4K panel with a 282-PPI pixel density probably won't be enough to make me lug around a nearly seven-pound laptop. That said, the combination of the high-density display, quad-core CPU, and fairly speedy mobile GPU should make this a nice productivity and light gaming machine. If you're on the road a lot, that may be a good combination.
Acer expects the 4K Aspire V Nitro Black Edition to be available at Amazon, the Microsoft Store, Newegg, and TigerDirect later this month.