You may take your cases with you and replace them with inexpensive plastic ones. However, it is best to stipulate with the buyer before the sale that you will be taking your covers with you, as he may have a potential claim that his purchase includes the home and all its fixtures.
Of course, if the covers are silver or obviously expensive in another way, you could easily counter claim that they were clearly personal items that he could not expect to be included in the sale. Even so, it is best to be clear about your intentions to avoid later misunderstanding.
 Sha’arei HaMezuzah 19:5, citing Mezuzas Melachim, Halachah L’Moshe 193.
 Agur B’ohalecha 42:31.