You can acually buy them today - Dasung did manage to productivize them enough for people to try them out. But it's really hard to compete on price, especially with consumer 27" 4k display costing 100-200$.
Pricey, small and really not the best design, but it's a start. I say it's a start but at the same time I'm afraid this is the best we're likely to get, given that the e-ink market is not growing and the technology isn't competing with cheap LCD screens and tablets.
A shame; I wouldn't mind a modern, affordable take on the typewriter with an E-ink screen (13 or 15 inch) and mechanical keyboard. I could probably build one if I have a lot more expendable income and time.
We tested 8fps video on our devices a while back and in the end you're getting a B&W display with 8 FPS updates... Why wouldn't you go for something like LCD or OLED instead? I don't believe you can beat LCD at being LCD.
There are other technolgies that promise fast update times, that offer similar characteristics (look into ClearInk), but they are nowhere near where E Ink is in terms of maturity.