Can you install cataclysm on wow when you have a private server

It is currently not known what effects it will have to install Cataclysm and using a private server.
Since the world-changing events of the coming patch 4.0.3 will change the world completely, it is possible that any WoW client upgraded to 4.0.3 or higher can no longer access or run when connected to a private server that is not also 4.0.3.