General Motors design chief Ed Welburn says all vehicles won't have that homogenous shape last seen in the 1980s.
He says fuel economy will have a "huge influence" on design but a positive one.
"How design can affect that is in the efficiency of the design, in its size and in the aerodynamics of the vehicle," Welburn says.
For instance, he says, the hard edges on the front of Cadillacs haven't hurt vehicle aerodynamics.
"We've been able to do very low-drag designs and retain the hard edges on Cadillacs," Welburn says. "The hard edges on the rear are a huge advantage.
"The proportions may change a bit. The tails may get longer. I think we'd look at the overall height of the vehicle. If you can bring it down, reducing the overall frontal area, that would help."
Of course, those elements would require big changes in vehicle architectures.
"You've got to get the hood down lower -- if you can do that, you can bring the occupant down," Welburn says. "Then the roof can come down, but it all has to work in harmony. It takes great collaboration between design and engineering."
BMW's Habib says aerodynamics is changing the brand's entire approach to styling new vehicles.
"We are embracing certain things we ignored in the past," he says. "Like how do you treat an arrow edge in the rear of the car or the spoiler? The surface in front of the front wheel has to be at an angle to flow along the body."
Habib says some of the solutions will be seen on show cars debuting at the Paris auto show, which opens this week.
"The way we design the rear of the car has changed a lot," he says. "For instance, we used to use an aerodynamic edge just on the taillamp. Now we are experimenting with taking them out of the tail and putting them on the body below."
Kia's Kearns says, "Wheel design is one of the first things manufacturers go after to save weight," reversing the trend of wheels getting larger and larger.
"We have to find a way to give a certain look to a vehicle that looks modern and fresh but also doesn't fly in the face of functionality and the weight," he says. "We're going to find a way to make wheels of a large diameter, but the thickness may change. Or maybe there will have to be lightweight materials or lightweight tires that don't add weight."
New powertrain technology will have an influence. Mazda's Jenkins says downsized engines and transmissions may let designers create vehicles with smaller front and rear overhangs with longer wheelbases.
He says the Tesla Model S is an example.
"The batteries are all in the floor. The car has a very small front overhang; its hood is low to the ground because of the small engine, so they're getting a very, very contemporary expression for a sedan and very dynamic overall proportions because of those technologies."
Christopher Weil, director of BMW's DesignworksUSA studio in Newbury Park, Calif., says the choice of exterior materials will begin to have a strong influence. For instance, BMW's new i subbrand vehicles with their carbon fiber bodies would look totally different if they were done in aluminum and metal. Sheet metal isn't as strong or thick, and "it has a different criteria the designer has to play with," he says.
Mark West, chairman of transportation design at the College for Creative Studies in Detroit, expects more glass and new materials -- including inside where translucent and mesh fabric could be used -- as cars become more lightweight.
Geoff Wardle, director of advanced mobility research at the Art Center College of Design in Pasadena, Calif., predicts there will be fewer "gratuitous and overstyled cars" than have debuted in the past three to four years.
Toyota's Scion cars, the Nissan Juke and even some General Motors SUVs and crossovers were designed with stretched lamps, bulges and other exaggerated features in an effort to differentiate them, Wardle says.
"I think the pendulum will swing the other way," he says.
He cites Volkswagen and Audi as two brands that resisted the trend.
"Audi is handsome and quite restrained," he says. "The VWs that are on the market are almost very plain in their appearance, but a lot of attention has gone into the detail and they are fairly refined. We will see some more of that."
J Mays says Ford won't follow the trend of so-called jewelry -- LED patterns and unique shapes -- in headlamps and taillamps but rather will make "lamps that reflect the technical object of what they're there for."
He says: "There are some excellent examples of high-tech headlamps. And there are some that are simply jewelry. Headlamps aren't jewelry. They're headlamps. They are supposed to shine light down the road. If you overstyle a headlamp, nothing gets older faster."
Mazda's Jenkins says automakers will be more expressive in designing front ends. He says grilles will be more three-dimensional, with trim and brightwork becoming more central to an overall look rather than just accenting a design.
Lighting will be a major enabler.
"As headlight technologies improve and become smaller, the headlight assembly can be broken up," Jenkins says. "You can have a much more slim and precise headlight graphic for example, whereas today, the basic headlight scale and size is still quite large."
Smaller lights mean extra space, giving designers greater creative flexibility in how they choose to integrate headlights into designs.
"You've seen this trend on concept cars for several years now, but we're on the verge of being able to realize that," he says.
Still, some independent designers aren't so optimistic about the overall trend in vehicle styling. Roberto Piatti, CEO of Italy's Torino Design, doesn't see a design revolution in the next four years or even further out.
"We are living in a strange time," says Piatti, who has worked on concepts and production cars for many European carmakers and Chinese brands.
"Carmakers don't want to create a strong break with the past," he says.
Piatti says carmakers "are scared of shocking the customer, and this means cars are going to remain pretty much the same."
A big factor, he says, is the growth of new markets around the world that have yet to develop sophisticated national style appreciation.
"New markets do not have independent taste, and they follow what is established and this moves everything in the same direction."
Of course, design is ever the moving target. What will we see on the new cars debuting in the fall of 2016? Inside the studios, that's already old news. What they are really thinking about is 2020.
Bradford Wernle contributed to this report