DEATH VALLEY, California — Toyota engineers were caught testing a 2010 Sienna prototype in the hot desert this week, and judging from the rough rear sections of the minivan mule, the future Sienna is likely to undergo a full redesign.The current-generation Sienna has been on the market since 2004, receiving just a minor refresh in 2006. With a 119.3-inch wheelbase, the 2009 Sienna provides a class-leading 149 cubic feet of cargo capacity, and it's unlikely Toyota will want to move away from that distinction.No engine specifications have been released for the future Toyota Sienna. The current model comes standard with a 266-horsepower 3.5-liter V6 and front- or all-wheel drive in seven- and eight-passenger configurations.What this means to you: Ford has moved away from minivans with its new Flex crossover, GM with its seven-passenger Buick Enclave/Saturn Outlook/Chevy Traverse trio. But Toyota will continue to challenge the popular Honda Odyssey for the minivan crown. — Kelly Toepke, News Editor