Spotted this post in the Lotus Developer Domain forum from David Marshak, Senior Product Manager, Real-time Collaboration.
“RE: Sametime 7.5: Release date ? Beta version ?
Posted by David Marshak on 29.Jan.06 at 13:47 using a Web browser
Category: GeneralRelease: 7.0Platform: All Platforms
Release this summer, beta is Mar/Apr”
The full thread can be found here