I recommend waiting; however, if you are certain that the only change to the W-2 will be the addition of an entry in Box 12 with Code W for an HSA contribution, then will be OK going ahead and filing. In this case you should go ahead and check the corrected box for your W-2 in TurboTax. If any other W-2 boxes, such as 1 & 2 will change or if you are unsure, you should definitely wait until you receive the corrected Form W-2.