Car Wars: A new hope ... for Detroit

(Fortune) -- For three decades, Japanese manufacturers have been chewing through the U.S. auto market like termites in a lumberyard. Led by Toyota, Honda, and Nissan, they now account for more than 38% of sales.

But that rapid advance may be coming to an end. Reason: Japanese product cycles are generally converging to the industry average. They are churning out new models no more quickly than everybody else.

That's just one of the surprising conclusions in the latest edition of "Car Wars," published by Bank of America Merrill Lynch's chief auto analyst john Murphy.

Car Wars is an annual study that assesses the relative strength of each automaker's product pipeline. Its thesis is that the rate at which an automaker refreshes its product line is a major determinant of its market share. In other words, the manufacturer with the newest car line wins. Over the last ten years, automakers with the highest replacement rate and the youngest showroom age have gained sales at the expense of competitors.

The end of a 30-year trend

What's going to hold back Japanese growth in the future, Murphy writes, is its slowing rate of replacement.

Honda (HMC) leads the industry with a planned 129% replacement rate between 2011 and 2014.

But Toyota (TM) is below the industry average for the next four years. And the average annual replacement rate for the Japanese of 27% is in line with the rest of the industry. Concludes Murphy: "We don't expect Japanese OEMs in total to carve off large chunks of market share, ending the trend of the last decade."

Europeans are also laggards in the survey. As befits their concentration in the upper reaches of the car market, they have a slower-than-average replacement rate. Some 46% of their new models are in the luxury and sporty car category versus 10% for the industry as a whole.

One popular-priced brand will be getting a lot of attention though. Volkswagen is opening a new plan in Tennessee and has some very ambitious goals for volume. It could be headed to dethrone Toyota as the world's largest automaker.

A big question mark is how some famous European brands will fare under their new owners. Volvo, Saab, Jaguar, and Range Rover have all changed hands in the past 24 months.

Two out of three ain't bad

The Car Wars report contains relatively good news for two of the Detroit Three.

General Motors' product launches should stabilize the market share of its four remaining brands near their current levels. Through May, GM was running at a rate of 18.7%. That's well below its historical average, but after losing share for 50 years, the automaker would welcome a sign that its share losses have leveled off.

GM remains primarily a truck company, though, which could handicap it if gas prices rise. The launch of its next-generation large pickup in 2014, along with a new Suburban, means that 44% of GM's new models over the next four years will be light trucks, versus 21% for the industry as a whole.

Propelled by a higher-than average-replacement rate, Ford (F, Fortune 500) is expected to continue to gain share, ultimately settling in the 17% to 18% range. It is running at a 17.4% rate this year.

Ford is going heavier than other manufacturers into crossovers. The Explorer moves from a truck frame to a car-like unibody construction later this year, while a European-inspired crossover called the Grand C-Max arrives in 2012.

Like everybody else in Detroit, Murphy isn't expecting much out of Chrysler. A relative lack of investment by previous owners means that its annual average replacement rate over the next four years is 24%, below the industry average of 27%.

But the numbers don't reflect the impact that Fiat CEO Sergio Marchionne is making on the company. Marchionne is pushing Chrysler to move faster than it ever has before and to get creative in its design and marketing.

While Chrysler isn't full-out replacing a lot of volume, it is touching up many of its models. If advertising can create buzz, and customers pay attention, Chrysler could surprise some people.

Its first test is looming with the launch of the all-new Jeep Grand Cherokee. One of Chrysler's highest grossing vehicles, it must sell well for Marchionne's turnaround to succeed.