As land becomes more valuable and there are more people needing burial plots, old cemeteries will be dug up for new bodies to replace the old. Think this is not possible? It is already happening (or soon will be) in Cape Town, South Africa.

Graves have been "moved" all over North America. Old family farms with their family plots, gone. Old local churches with their small cemetery plots, gone. Replaced with roads, assorted buildings. Moving or replacing old graves for new might be a little less heard of, but I'd be surprised if it were entirely new.