There is no indication whatsoever in the plans detailed in the NPS documents that there is any intention of closing the parkway to bicyclists. In fact the proposals being made explicitly state that the parkway and surrounding roads will continue to be open to bicyclists and provide an outstanding opportunity for cycling.
Lemond Reno, Giant CFM 2, Lotus, Haro (for the trainer)
I was just at the Blue Ridge Parkway visitors center on Saturday (3/10/12) and spoke to the ranger (I guess he's a ranger) about riding my bike on the parkway. He had a special hand out for cyclists and did not mention anything about closing the Parkway to cyclists. So, I think there's nothing to worry about.