Tesla Inc.’s plans to pad its lineup of electric cars are taking shape, with Elon Musk sketching out a timeline for the arrival of a semi truck, pickup and sports car. After unveiling the finalized Model 3 sedan in July, Tesla will show a semi truck in September and a pickup in 18 to 24 months, the chief executive officer said in a series of tweets Thursday. The Palo Alto, California-based company also will bring back the Roadster, its first model, as a convertible. “Team has done an amazing job,” Musk wrote of the semi truck. “Seriously next level.” Tesla shares climbed as much as 2.7 percent as of 2:21 p.m. in New York trading, valuing the company at about $49.7 billion. Its market capitalization briefly passed General Motors Co. earlier this week.