Retailers seemed almost surprised that designers had managed to cram so much style into classics like the coatdress without overdoing it. As Mr. Frasch said, “It’s fashion, but it’s not going to be going out of fashion.” Julie Gilhart, the fashion director at Barneys New York, brought up the Lanvin sheath with the twist, which will cost about $2,300. “It’s the kind of dress you can wear, then put away in your closet for 10 years. When you bring it back out, people will say, ‘What is that?’ And you can say, ‘Yeah, it’s a 10-year-old Lanvin.’ ”