GM Design Director Ed Welburn as the Buick Avenir makes its unexpected debut.

By the time the official auto show news conferences begin, automakers have usually signaled what they have coming. But a few surprises manage to sneak onto the schedule, one of them coming from Buick in the form of the Avenir, a boat-tailed sedan that could soon become the resurgent Buick’s new flagship.

The new sedan is intended to underscore the dramatic changes that are helping remake a brand that seemed all but certain to disappear when General Motors plunged into bankruptcy back in 2009. Officially dubbed a “concept,” the sedan apparently shares the same underlying platform as the CT6, the premium-luxury model that Cadillac plans to bring to market in 2016.

“This car does a god job of showing everything that we’re doing in the Buick studio,” said Ed Welburn, GM vice president of design, during a Sunday night media preview of the Avenir. “I just love walking into the Buick studio,” added the styling chief, who noted that the youngest members of GM’s design staff love working on Buicks.

That’s a far cry from the way Buick was treated as an outcast brand not all that many years ago. Of course, it helps that it is now delivering record sales, largely because of its success in the booming Chinese market.

“Design has become the great differentiator in the market,” stressed Welburn.

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Expect a production model to pick up on key cues of the Avenir within the next several years.

The Avenir is described as a flagship sedan that explores progressive design, along with advanced technologies for comfort and connectivity, GM officials said.

The Avenir is distinguished by its premium sports proportions and all-new interpretations of traditional Buick cues – including a modern take on the portholes that were once the brand’s signature. A long hood, wheels-at-the-corners stance and a sloping, rear deck that pays homage to historical models, such as the Riviera, distinguish the Avenir’s proportion.

Mark Reuss, GM’s executive vice president for product dcvelopment, said the Avenir sits on GM’s Omega platform, which also will be used for the Cadillac CT6, the full-size luxury sedan being prepared as part of the Cadillac Division’s planned revival.

However, Reuss insisted GM doesn’t have any plans to produce the Avenir. Nor is it targeted at the Chinese market. “The Chinese and U.S. markets are converging. We’re not going to develop separate cars for the two markets.  We’re just putting the Avenir out there to see the reaction. We’re going to see what you all write about it,” Reuss said, after the concept’s unveiling.

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Nonetheless, those attending the Sunday unveiling couldn’t help but get a sense GM would like to put something like Avenir into the Buick line-up.

“Avenir,” said Welburn. “demonstrates the growing international reach of Buick and offers an exciting vision of where it can go.”

“The vehicle remains unmistakably Buick with a modern take on the traditional Buick cues such as the sweep spear and boattail. The result is a piece of artistry that is precise in its character, beautifully proportioned. It really takes your breath away,” added Michael Simcoe, vice president of design, GM International Operations.

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The Avenir grille puts a new face on the brand, noted Simcoe, recalling that it is, “a modern interpretation of a design introduced on the landmark 1954 Wildcat II concept, which shattered expectations of what a Buick was supposed to be.”

Whether GM will shatter expectations again by finding a way to put Avenir into production remains to be seen, but it is clearly looking to gauge consumer reaction at the Detroit Auto Show and other shows to follow.

(Paul A. Eisenstein contributed to this report.)