Adding new feature classes to one end of a replica would not qualify as a 'schema change'. You will need to recreate the replica to include the new feature classes. (or you can add new feature classes programmatically: How to add a feature class or table to an existing replica.)
There is a sample GP tool on the Geodatabase Code Gallery that will add datasets to an existing replica (the code from the Dev help topic that Mandar referenced is used to implement these tools)
There is a second gp tool that will Sync schema changes to the relative replica, and sync the data in one process. This tool may be of use to you also.
