According to the Associated Press, the Japanese Yomiuri newspaper is reporting that the new Prius spin-off will be available in late 2010, carrying a base price of $22,000 (slightly less than a 2010 Prius). It'd be interesting to see how such a model would work in Japan, seeing as Toyota already sells the Prius and Sai (a version of Lexus' HS 250h sedan) in that market.
The new model may also use lithium-ion batteries in lieu of the nickel-metal-hydride batteries used on the current Prius. Toyota is reportedly developing said battery cells with Panasonic, its longtime collaborator in battery and EV technology.
Source: Associated Press