Look at the following for some early information of what’s coming in OCS 2007 R2 that is to be released in late January 2009.
I’m not sure of all your telephony needs but it might actually solve many of them quite good.
Enhanced Voice and Mobility
•Attendant console and delegation. This allows receptionists, team secretaries and others to manage calls and conferences on behalf of other users, set up workflows to route calls, and manage higher volumes of incoming communications through a software-based interface.
This replaces the Communicator Client for a receptionist, administrative assistant they can perform blind transfers, consultative transfers, import their bosses contacts, pre-stage recurring audio meetings, etc.
•Session Initiation Protocol trunking. This feature enables businesses to reduce costs by setting up a direct VoIP connection between an Internet telephony service provider and Office Communicator 2007 without requiring on-premise gateways.
I can see a lot of interest here since you can save quite a bit by using Direct SIP vs. using on-premise hardware such as a Session Border Controller. We are working as part of the SIPConnect working group to ensure there is fully interoperability with OCS.
•Response group.A workflow design application manages incoming calls based on user-configured rules (e.g., round-robin, longest idle, simultaneous), providing a simple-to-use basic engine for call treatment, routing and queuing.
This can be used for simple call group queuing/routing such as a departmental IT group it also has hold music, autoattendant speech recognition such as “Say ‘Printers’ for Printer support” and the recipient will receive an inbound call with a contextual reference such as “Printer help”.
•Mobility and single-number reach. This extends Microsoft Office Communicator Mobile functionality to Nokia S40, Motorola RAZR, Blackberry and Windows Mobile platforms, allowing users to communicate using presence, IM and voice as an extension of their PBX from a unified client.
More information and source