At the 2010 Los Angeles Auto Show, Nissan has unveiled a concept design that points the way toward some of its next-generation sedan models—even though Nissan swears that its Ellure show car is not “intended as preview of any upcoming production model,” in the words of Shiro Nakamura, Nissan’s chief creative officer.Instead, it’s “an expression of [Nissan’s] long-term vision for the next