There are some worries that the Bush tax cuts expiration in 2011 might lead to a double dip recession. I would agree if that were to happen the economy will get hit hard but I dont believe that will happen, at least not fully. Christina Romer and probably Larry Summers would advise Obama a net tightening of fiscal policy if the economic conditions were still weak, Geithner(if he is still around late in the year) is likely to be in the same camp as well. They all know what happened in 1937(heck Romer wrote an article on the economist 'Lessons from 1937', Geithner as a central banker has probably read the Japanese 90's literature), so yes the Bush tax cuts might expire but the WH is likely to propose tax cuts in other areas, so the net tax hike will not be as as huge, even if there is one
In fact, I suspect they will implement those through some kind of new stimulus package. With the UR rising and elections coming, there will be a growing pressure for those