Yeah, Airfoilmod is right and Also, there is always a prestige and pressure issue.....777s are marketed by Boeing as their Flagship, and grounding all of them with RR Engines on a global scale, will be a major disaster especially when 787s is delayed and Boeing is offering 777s as cheaper alternative to fill the 787s gap.......
....so imagine where will Boeing stand if FAA/ NTSB ground all the 777s???? IT will never happen as far as I can see............Safety is for people like you and me who believe in it.......try explaining it to some top Bean Counter of a Mega Company.........they just know how to convert everything into Dollars or Euros or Pounds