I’m not so sure. While PotO has its share of lavish design and production values, it is still a much smaller work (in scale) than LM. Think Chicago (some period piece, but also heavily stylized with one main set as a centerpiece) vs. Evita (casts of thousands, epic battles, more history and less romance, etc.).
Madonna’s Evita, despite having debatably the biggest female star in the world, did not do very well financially. It didn’t make its costs back in the States, and it was a huge enterprise mired in pre-production wrangling for years and years. And even the ALW/TR musical didn’t have as many characters and plot threads than LM does. The sheer logistical challenge of adapting and staging it would be more than most financieers would be willing to invest in (especially since it’s not like LM is exactly a surefire property, its B’way popularity notwithstanding).
PotO would have to be huge to overcome the trepidation that naturally emerges when conronting the Hugo project. I’m sure someday there’ll be an adaptation, but it’ll probably be a high-risk labor of love. The success of one or two recent musicals doesn’t automatically equate to Box Office Gold (especially when 19th-century French politics is your subject matter)