I think they're still struggling with durability. I think it's likely we'll see rollable phone screens of sorts within a few years though. A rollable screen could just be an extension screen that could be pulled out when needing more screenspace
I'm trying to think of where I've seen this in TV and movies. Final Fantasy: The Spirits Within (IIRC) and there was a TV show where some Asian man had a plasma gun embedded in his wrist or something. Aliens were involved, and their cell phones all had roll up screens.
That's basically an extension of how current bendable screens work, right? Just with the whole thing bending instead of just the middle.