As Robingen said, there's no way to set a time line unless you going to get technical and measure your body fat.
You can use Ketostix sticks to measure the fat burning process on daily bases, except it wont be limited to belly fat only.
I would also advise doing more resistance training; i.e. stairs. If you can run 4 km daily, then push yourself harder and run 5 or 6 km.
I'm on crazy plan to lose weight
April 01, 2013 = 343 lbs.
May 01, 2013 = 313 lbs.
June 01, 2013 = 290 lbs.
July 01, 2013 = 273 lbs.