Boeing’s plant in Charleston, S.C., just had the most dramatic week in its history, a week that made it seem that the sky is the limit for the future of the five-year-old plant. On Feb. 15, plant workers voted overwhelming not to join the International Association of Machinists, seemingly reaffirming right-to-work South Carolina’s success in 2009 in luring Boeing here, far from the Washington workers who had built all of its legacy commercial aircraft for decades.