Those NO VACANCY signs could be relegated to the dustbins of history. According to new research from McKinsey & Co., the hospitality industry could be reeling from COVID-19 for years to come.    In early May, occupancy was less than 15% for luxury hotels and around 40% for economy.    Looking ahead, McKinsey expects economy hotels to have the fastest return to pre-pandemic levels, and luxury and upper-upscale hotels to have the slowest. Due, in part, because economy hotels are better...