I'm seeing as many as ever(I drive local for a national battery company). I am *noticing* more McCain stickers, and a LOT more Palin stickers :) than I did before the election, but that probably owes more to chance than anything else.
As a general rule, people don't remove stickers here in Arizona(I think they generally don't care for their cars as well here as in other parts of the country). I regularly see bumper stickers(generally on neglected turdmobiles, but still) from the 2000 election, and FREQUENTLY see them from the 2004 election. Kind of a fact of life. Liberals - and I don't mean to be snarky here, just observing - seem to wear their "Kerry-Edwards '04" stickers as a badge of honor.
My daily driver may be a 24-year-old $800 Celica, but I still can't bring myself to deface any of my automobiles with a bumper sticker, however worthy the libertarian cause may be.