Hmmm...I must say this is my favourite idea. It covers the preservation angle as well as the clean slate angle. While I think the buildings would do just as well as landfill, if a compromise has to be made, this is the one I would prefer.
It would be expensive, but a great idea. Save the most important elements of the buildings (i.e. the entrance archways, terracotta tiles). Recycle the brick (old brick, depending on its condition is quite beautiful) and store the elements until they can be resurrected in due time. It's what they did in Edmonton and it's much better than just demolishing and forgetting.