Titantic was already a musical... It ran on broadway from '97-'99... though it wasn't based on the movie (obviously, considering it hit the Great White Way before the movie came out)
I stand by my comment earlier that Broadway needs to start producing more original shows with original scores... I'm looking forward to the arrival of Spring Awakening and Curtains (which will take place of the Wedding Singer). The Producers will also be closing soon, only to be replaced with another Mel Brooks movie turned musical, Young Frankenstein... hopefully this is all just a fad and will soon pass