Actually there are two laptops, both with a slightly vague release date of "Mid 214". They stay with the standard-but-we're-not-sure-why size of 15.6" and have a native resolution of 3840 x 2160, giving a spatial resolution of 282 pixels per inch. That's almost enough to need a microscope.
This is a high-powered machine that is nevertheless not too bulky. It's aimed at engineers and it will, we would imagine, be pretty good for video production as well. It includes an NVIDIA Quadro K2100M GPU that seems well up to the job of powering a 4K screen and the sort of applications that will be running on it.
With more of a focus on styling and portability, this has the same size screen as the W50, but with edge-to-edge glass and a touch-sensitive screen.
We think this is less of the start of a trend than the starting gun for every other manufacturer. Even though screens of this size are really to small to do full justice to 4K (people compain that they can't tell the difference between HD and 4K on a 50" screen - but you do sit pretty close to a laptop display) that's not going to stop the deluge of 4K laptops that will follow this first step by Toshiba.
And we look forward to it. Because whatever else you may think, this is only ever going to improve the image and usability of your laptop, as long as your application's menus don't start appearing in 0.79 point Helvetica.
There is a precident for this small-pixel mania: with smartphones now routinely sporting Full HD screens, if you put four of them together, you'll have 4K in a space the size of an iPad screen. Speaking of which...