Timing is everything. If the Clintons want to sink Obama, expect early next week as the time to make maximum impact. Dominate the week’s news cycle and leave Obama just a weekend (which is typically not an effective time) to bounce back before election day.
Hillary announced she may not leave after this term, as originally stated, so I doubt she will sink him before the elections. She's biding her time until after the election, specifically Nov. 15th, when Congress will take up hearings. If Obama loses it will be a blood bath.