It' not unusual for the Dutch Investigation Board to take a long time before publishing the final report. Intermediate reports are only published if there is an urgency to it. Most reports take two to four years to complete, some much longer.
For example the investigation into runway incursion by a Boeing 757 on January 29, 2004, was not closed until August 11, 2010. So that was only 6.5 years for what they call a "short" investigation.
The investigation into the incident of February 10, 2010 will be a "full" investigation, let's hope that hasn't any bearing on the duration.