Sony has demonstrated a 4" Rollable OLED Display at the at the SID 2010 International Symposium. While only a prototype the 432 x 240 pixel resolution display supports 16M colors while exceeding 100nits brightness and a 1,000:1 contrast ratio.
No word if or when this will ever come to market but pencil sized cell phones can't be too far in the future.
More at PC Watch (in Japanese)
