They're calling it the Zephyr.
two of Plastic Logic's 10.7" screen panels to produce a surface area that measures 15.4" when laid flat. Each panel has a resolution of 1280 x 960 pixels, giving the Zephyr an impressive 1280 x 1920 resolution (minus a pixel or 2 for the fold).
Correction: A reader noticed that there is an extra seem in the device shown below. The Zephyr has 4 screen panels, not 2, making this a 21.4" ereader with a resolution of 1920 x 2540. Thanks, Tom!
Okay, that's not so impressive when compared to say the Kindle Fire HDX 8.9, which has a screen resolution of 2560 x 1600 in under 9", but the Zephyr is still larger than any previous ereader. And at 150ppi, the sharpness of the screen(s) on the Zephyr matches that of Sony's 13.3" writing slate.
Update: I ran this idea by a construction engineer I know and she would never buy it. It's too fragile, too costly, and everyone has already gone digital. They're using pro grade tablets to display blueprints, so there is no need for this funky device.
There aren't any details yet on connectivity, but the Zephyr will be equipped with a touchscreen to make manipulating blueprints easier. I for one would love to see how they managed a touchscreen with a fold down the center; that is probably the most technically complicated part of the design.
There's also no firm details on price or release date (nor would you expect any at this point), but according to Plastic Logic the Zephyr prototype will be on display later this month. Printless Plans and Plastic Logic will have the Zephyr on display at the GreenBuild trade show in Philadelphia, Penn. It should be possible for attendees to play with it and try to kill it.