The original iPad enabled users to lock the rotation, so that when you held the iPad in a different orientation, it didn't rotate around to self-correct. But in iOS 4.2, Apple transformed the purpose of that button to mute the sound on the device. It looks like in the new beta, however, users will be given an option for the button and will be able to choose one behavior or the other.
Announcing iPhone support this week, Verizon promised the ability to use the iPhone for a Wi-Fi hotspot that supports up to five devices. The new iOS explicitly supports that feature, and gives users the option to turn it on and off. That it's built-in suggests other carriers might support the feature.
The new iOS also gets a smattering of very small features, including the ability to set the number of SMS alert tones to up to 10 times (before giving up and remaining quiet). The look of the keyboard is slightly different. There's a goofy new font called "Noteworthy." Advertisers will be given the option to display full-screen ads in iAd.
It also appears that the new iOS won't work on the iPhone 3G or the 2nd-generation iPod Touch (the current version is the 4th generation).
You can never know for sure what Apple is going to do next. But mysterious, cryptic clues in the new beta of iOS 4.3 is solid evidence of future directions.