No.. not a typo. According to PC World, Prodisc will be unveiling 4.9GB discs at Computex.
The catch is that its supported by only 15 drives:
Behaviour Tech Computer's (BTC) DRW1108IM
LG Electronics' GSA-4082B and GSA4120B
Lite-On Technology's SOHW-1613S
Pioneer's DVR-107D and DVR108
Plextor's PX-708A and PX-712A
Samsung Electronics' SH-W08A