The telecom and networking research company also reported that driven by expanding demand, VoIP continues to gain in popularity for all businesses, regardless of size.
"Large enterprises have led the way in the deployment of IP telephony, and now we are seeing small and mid-sized business also realizing the benefits of VoIP," said Alan Weckel, analyst at Dell'Oro Group.
"Large enterprises are now testing the waters with Unified Communications solutions that promise to provide users with a cohesive communications experience in which voice, instant messaging, video, and email are integrated together," Weckel said.
According to the forecast report, PBX market revenues will continue to grow over the next five years primarily on strong sales of IP PBXs.
Other PBX segments are not expected to fare so well by 2011. Hybrid IP/TDM PBX revenues are predicted to decline starting in 2010, and by 2011, traditional PBXs are projected to make up less than 5% of the total market revenues, a steep decline from 2002 when the traditional PBX segments accounted for more than 85 % of market revenues.