If you have not upgraded to iPhone OS 3.0 yet, the next iPhone OS upgrade should be coming with version 3.1. While there is no change log available on the new version, it should include numerous bug fixes and the mms feature is said to be turned on by default even if you are on AT&T network. We will keep you updated once we have the information on the detail change log.
iPhone SDK 3.1 beta and iPhone OS 3.1 beta are now posted to the iPhone Dev Center. These versions are for development and testing only and should be installed on devices dedicated to iPhone OS 3.1 beta software development. Please read the iPhone OS Pre-Install Advisory and the iPhone SDK 3.1 beta release notes before downloading and installing.
iPhone OS 3.0 was just released 2 weeks ago, with the addition features like copy & paste, mms (depends on your regions) and landscape keyboard.