No matter what the result of the November elections, the US is, almost certainly, not going to keep flying the Shuttle after the ISS is complete, and it is doubtful that NASA or the Congress will want to keep paying for ISS operations after 2016 or 2017. International negotiations will decide the future of this $100-billion asset.
This article says privatization is the most likely option:
Yet, a traditional privatization would probably be as unacceptable as an [European Space Agency] takeover. If there were an auction, an investor might be able to take over the ISS for pennies on the dollar. Even if he or she paid $10 billion for it, that would still be roughly ten percent of what it cost to build. None of the governments involved would want to explain publicly why they spent $100 billion for such a pitiful payoff.
The port authority model, which has been proposed by Rick Tumlinson and the Space Frontier Foundation, makes sense to American ears, but may not be as acceptable to the Europeans or Russians. They would probably prefer a more traditional model of a state-controlled company or a public-private partnership.