We love auto show surprises, and Buick has already gifted us a sparkly package on the eve of the 2015Detroit Auto Show. Dubbed Avenir, this four-door concept is said to signal the future of the Trishield brand by previewing a possible flagship sedan.

Incorporating time-honored Buick design hallmarks like the sweep-spear profile, Ventiports, and even a subtle boattail rear-end, the four-place sedan is powered by a surprisingly real-world powertrain – namely a next-generation V6 with cylinder deactivation and stop/start, with the most interesting part of the driveline arguably being a “twin-clutch all-wheel-drive system” and a nine-speed automatic gearbox with paddle shifters.

Make no mistake, this is a big car. At 204.5 inches long, it’s longer than a standard-wheelbase Cadillac Escalade – a span that’s emphasized by the car’s long hood and waterfall grille – though it’s not quite as wide.

While clearly a showcar, the beautifully crafted interior looks largely produceable, including attributes like a next-generation 12-inch touchscreen infotainment system and 4G LTE wifi, but we suspect a production car would pick up a third rear seatbelt and give away some of its flowing contours that are said to have been “inspired by nature and sea waves receding on a beach.”

No word yet on whether there’s actually a showroom future for a car like this – it could simply be an exercise designed to test the waters for a next-generation LaCrosse. After all, sedans aren’t exactly popular concept fodder these days, especially as crossovers continue to eat into traditional sedan sales in many of the world’s markets. However, China still loves the coddling rear seats of a proper four-door sedan (which in this case include silk and bamboo elements), and with a majority of Buick sales happening in the People’s Republic, the Asian nation controls the destiny of this General Motors brand. Said another way? Anything is possible, especially with General Motors known to be working on a large flagship sedan for Cadillac already – the Avenir is reportedly based on the same Omega architecture that will underpin the forthcoming CT6.

What do you think? Is this a promising direction for the resurgent Buick? Scroll through our gallery, check out the video, and then have your say in Comments.