No, nothing in life is for sure, however, getting a 601A waiver approved make the process easier for you. If you are granted a provisional waiver, however, what it does is to give you reassurance before you leave the U.S. that your unlawful presence will most likely not be used as a reason for denial of your immigrant visa. The waiver a approval also saves you time: If you pass your interview and are approved for your green card, you will probably only need to stay outside the U.S. for a few weeks. Even after the provisional waiver is granted by USCIS, the U.S. embassy or consulate could still deny your immigrant visa and green card for reasons that have nothing to do with your unlawful presence. It may be that you have had some other problem in your life such as past criminal convictions or a communicable disease that was discovered after you took your medical exam. In these cases you may qualify and apply for an additional waiver. Also, if you are suspected of marriage fraud or if your marriage fails before you receive your immigrant visa, your visa will also be denied.