If Sansa's flowering is cut out then she will need to marry Joffrey sooner as it was the only thing that was keeping her from marrying him in the first place. This meens the Tyrells might not want to aid the Lannisters in the blackwater, Mace wants his daughter to be queen, it was easy enough for them to call off a betrothal when something better came along but I don't know if it would be proper for him to drop Sansa for Margaery once they are already married. This meens that Stannis may win the blackwater, Mace might ally with Robb instead of Joffrey, Joffrey probably won't die without the Tyrells there, unless Stannis does indeed win the blackwater. Pretty much if Sansa does not flower, everything changes.