A large screen e-reader would be great because of the battery life improvements on e-ink displays. I would love to try a dual screen e-ink thing if one were to exist. I can't speak for other musicians, but to me as a piano player, I value reducing the number of page turns a lot. Slower pieces are alright, but with fast paced music the page turns happen too quickly. I tried borrowing an android tablet from a family member as pdf viewer for sheet music, but it didn't feel too great working with a single screen compared to what I'm used to. It's not a compromise that I'm willing to make.
I've considered getting a normal laptop and then attaching a portable monitor to get some more screen real-estate, but that's a second thing and more weight to lug around. Another thing on the list of ideas was a foot pedal for page turning, which I haven't tried yet.