I hope they’re not abandoning page turn buttons for good, like my Oasis has — the only reason I bought the Oasis. Touch screens are just not a good reading experience, for me.
Physical page buttons have a small UX disadvantage in that your finger must be located at the button when its time to turn the page. Unlike the soft method where you gently tap screen with finger or pen, and you're not limited to one activation location. So, more energy required with the physical button. I was disappointed at first the Scribe didn't have buttons, but now I don't care.
For one-handed reading especially, that alone makes physical buttons significantly more ergonomic, provided that they're placed such that your thumb rests on them naturally when holding the device.