4.6 introduces support for 3.3 and above firmware. It also removes support for firmwares below 3.1, as well as phones SPIP 300 and 500.
Admins will have to define the specify phone version when adding/configuring a new Polycom model. Firmwares currently supported are 3.1.X , 3.2.X and 4.0.X. In the future maybe finer grained versioning will be defined if necessary.