Toyota RAV4 has a better gas mileage, but not by much. It comes with the optional third row of seats. But getting to the third row may be a problem, and the seats themselves are not full size.
Toyota is working on an extended ‘wagonized’ version of Prius (it should be about the size of Mazda5), which may or may not seat seven, may or may not have three rows, may or may not be revealed at the Detroit Auto Show, and may or may not go on sale in the US sometime in the first half of 2011. Not much is known for certain yet.