Are you referring to Symposium Agent (and probably also Symposium TAPI)? If so, then current releases are Symposium Agent 2.3 and Symposium TAPI 3.0.
If you mean Symposium Call Center Server, then Release 5.0 is the newest. For Symposium Express Call Center Server, then Release 4.2 is most current.
There are other Symposium products as well. Let us know if you mean something else.