From the NPS website:
The Cades Cove Loop Road is scheduled to be closed to all public use from March 1-May 21, 2010 for repaving. Weather conditions may affect these closure dates.
The loop is in desperate need of repair. Not only is the road extremely rough, but there is not enough room to pass when all the tourons park in the middle of the road to take pics of a squirrel. The plan is to completely repave the road and existing pullouts, as well as increase the number of pulloffs. The hope is that these improvements will also help the park by reducing the erosion caused by cars driving off the pavement.
Personally I would like to see them initiate some sort of shuttle service, but I don't expect that to ever happen. I don't go near that place on weekends, but midweek typically is very peaceful.