The hospitality company is enlarging the MGM Grand Convention Center by 250,000 square feet, bringing it to a total of 850,000 square feet. That will make it the second largest convention space in MGM Resorts portfolio after Mandalay Bay. The expansion will be completed next year. MGM Resorts is aggressively expanding its convention space in Las Vegas as the U.S. economy continues to rebound from the Great Recession, giving companies and individuals more confidence to spend on trade show attendance.