Apparently some people are never satisfied. Even though he's got the Camry, the best-selling car in the U.S., Toyota Motor Corp. President Akio Toyoda grandson of the company's founder, is now pushing for an overhaul of Camry and Prius with an emphasis on "waku-doki" design, shorthand for the Japanese phrase for heart-racing qualities.

Getting it wrong could cost them. Bloomberg says it could knock Camry from its perch at the top, a title held for 12 consecutive years, and could see Prius, which sells more than 200,000 units annually in the U.S., eclipsed by newer hybrid vehicles.

The aim for the next Camry is a "more emotional, more impactful design," Kevin Hunter, head of Toyota's U.S. design studio, said in an interview at the Detroit auto show this week. "Camry's taken some hits on styling, but it's still selling well. But we need to create better design for Camry in the future."

"Finding the right balance is going to be very tricky" for the Camry, said Jack Nerad, analyst and executive editor at Kelley Blue Book in Irvine, Calif. "Most consumers like good-looking cars, they don't want to drive appliances."

Because Camry's customer base, which Toyota estimates at 5 million owners, is so large, there are limits to how far the company can go in changing the design, said Kazuo Ohara, head of Toyota's U.S. sales unit.

"I would not go so far as saying we could be adventurous, but at least more aggressive," he said. With the current Camry, "we were probably a little bit too conservative."

The emphasis on the next version of the car is enhanced interior packaging and materials and more "emotional" exterior looks, Ohara said, without elaborating on specific details. The company isn't ready to say when a new Camry or Prius will go on sale, the executives said.

Because the Prius' novelty has worn off, it too is under pressure.
As Toyota's designers refine the look and layout of the next Prius, they said they will need to retain the car's triangular profile for maximum aerodynamic efficiency and top-level fuel economy.

"The next Prius is in a difficult location in the market because hybrids already have become a fundamental technology," Tokuo Fukuichi, a Toyota senior managing officer and head of global design, said in an interview in Detroit.

"We have to try to make a 'future feeling' and 'best in the world'" fuel economy, Fukuichi said. "If we couldn't get the best mileage, we don't need a next Prius.