Are Federal Data Privacy Laws Inevitable?

The possibility of a federal data privacy law being enacted is once again in the news as Bill Gates said that there was a critical need for such legislation at a dinner hosted by the Center for Democracy and Technology. According to this article from CNET the Microsoft co-founder argued that the key was to put in place

explicit policies about where information can be used while at the same time having enough information to track down egregious behavior

and Senator Patrick Leahy stated that he was ready to re-introduce his Personal Data Privacy Act to try and achieve that goal.
However, the big issue, which neither Gates nor Leahy addressed, was whether there was a realistic likelihood that any data privacy legislation from Washington would improve data privacy practices, or whether the primary effect of such legislation would be to preempt tough state laws on the books today, such as California's SB-1386. While there is no sure way to know what will happen in Congress, my guess is that, if Washington enacts data privacy legislation, protections such as those afforded by California's law will be a thing of the past.