No construction timeline has been released, but hopefully it won't take long because that is a seriously scary prospect. Maybe consider taking the Manhattan and Queensborough bridges if you can instead. After the construction things will supposedly look nice and cleanly separated, like in the graphic at right. How exactly this separation will be achieved remains a mystery. Technically, there are already signs suggesting that the North side is for cyclists and the South side for pedestrians, but nobody seems to pay any attention—they're also covered with graffiti more often than not.
In other possibly promising news, Transportation Alternatives will be polling morning bike commuters tomorrow morning at the Manhattan end of the Williamsburg Bridge on their ideas and suggestions for improving the deadly Delancey Street onramp approach.