He won't. Bush has made this very clear. And isn't it interesting that he would spend his precious political capital on something that only advances the interests of Mexico and the cheap labor lobby instead of reforming Social Security? This speaks volumes about Bush's priorities and where he is coming from.
It amazed me how many people said, "He just needs the Hispanic vote. Just wait until after the election... then he'll get hopping on the borders!" Considering Bush's unchanging OBL stance, I feel kind of smug having told everyone, "Don't count on it."