A) Somewhere between now and Mid-September would be my guess but no one knows, not even Apple knows a specific date.
B) You have the option to trim video without trimming the original, copy and paste video, possibly mms when it is released as it currently has the options unlocked, voice control support for bluetooth headsets, and here are some of the other improvements
iTunes 9.0 was predicted to be released in september and I think that's when they would want to release 3.1. I could see them releasing a 9.0 pre release so we can test it since the changes could be big. 9.0 might also be needed to support something in 3.1, like 8.2 supported 3.0.