I doubt that Luigi would ever take the place of mario, as Mario is considered the mascot of the entire gaming industry. And besides, why would he take his place? Mario is known by almost everyone in the world who has played some video games. However, if Luigi did take Mario's place, then it won't really affect Nintendo. Sure, people won't recognize Nintendo by him, but it won't affect the cmpany, as the main thing that matters is the consoles/systems and games they make.