An update on what happened to the investigation:
An anti-terrorism court in Pakistan has charged two senior police officers over the 2007 assassination of former Prime Minister Benazir Bhutto. They were charged with security breaches and failure to protect her, prosecutors said.

Five alleged Taliban militants have also been charged with criminal conspiracy over Bhutto's death.
Link:http://www.bbc.co.uk/news/world-asia-15605565