Chinese electric vehicle (EV) producer Nio (NYSE:NIO) is scheduled to report earnings next week. Despite some high volatility, the company has performed well over the past month, although NIO stock remains down significantly for the past two quarters.The threat of tariffs imposed by the U.S. government has cast some dark shadows over NIO stock recently. But as shares rise on pre-earnings momentum, investors are likely considering an important question: Is this former EV winner on the verge of a comeback, or ...