From the Microsoft Dynamics CRM December 2012 Service Update and Beyond Partner Training Blitz today, we now have release dates for online and on-premise customers.
Update Rollup 12 will be pushed to existing online customers starting on January 1st and proceeds to completion on January 31st.
Update Rollup 12 will be available January 10th throughout the Microsoft Download Center and on January 22nd through Microsoft Updates.
Cross-browser compatibility (assuming all scripting is SDK-compliant) will be immediately available after Rollup 12 is installed. The updated end-user experience is opt-in.
The Yammer integration and iPad Sales experience service update will start in February and be globally deployed by February 28th.