I am also waiting on a PhD acceptance. Many, perhaps even most US schools will defer entry for one year. I am counting on the prestige of the Fulbright coupled with its funding for my field research to score me a deferment. Take a look at that option. Also, maybe someone else can address this or maybe the Fulbright website does, I assume you can always turn down the Fulbright later. Remember some awards are given as late as September which I bet is because of people withdrawing late.