[Quoth]

If there was any tablet with aspect of 3:4, 4:5 rather than 10:16 or 9:16 (worst) and about 8″ with at least volume buttons (able to be page turn) and a screen like the Nxtpaper (I think maybe two other companies have screens nearly as good), I'd buy it as a colour alternative to the Sage. Not Kaledio Colour eInk as it's too dark and not Gallery Colour eInk as it's far too slow, even if the resolution issue was solved (very bad on Kaledio).
The 9.7″ and larger are all to heavy to read for a long period of time, like 4 hours.

Edit
There are now displays even worse aspect than 16:9 (9:16 on portrait). Possibly acceptable for a phone as long as shorter ones are still an option.