According to a German blog, Microsoft plans to release Beta 2 Technical Refresh on the 14/15th September.

The blog also lists the following:

• Office 2007 Beta 1: 17.11.2005
• Office 2007 Beta 1 TR: 13.03.2006?
• Office 2007 Beta 2: 22.05.2006
• Office 2007 Beta 2 TR: 14/15.9.2006
• Office 2007 RTM: 25-28.10.2006 - Business customers -> volume licensing
• Office 2007 Release Date: 30.01.2007- Home Users -> Retail and OEM

The dates tie in with the expected release date and RTM of Windows Vista.

Volkan's Blog | Neowin | bink

Microsoft Office System Beta 2 Technical Refresh, Microsoft Office System