According to MacRumors iTunes will be updated to version 9.1 next month. Probably around the same time as the iPad’s U.S. launch this Saturday. Some new features and changes in 9.1 will be Books, Genius Mixes enhancements, Tweaked summary panes and Automatically songs converter.

Some more detailed explanation:

• “Audiobooks” entry in the iTunes Source list will be replaced with a broader “Books” section
• Genius Mixes enhancements that automatically selects songs that “go great together”
• Tweaked summary panes (including a move of the “Check for Update” and “Restore” buttons to the left side of the pane)
• Automatically convert songs to 128 kbps AAC format when syncing to devices

Source [Macrumors via FSM]