According to an individual familiar with the latest version of the iPhone OS simulator in the iPad's software development kit, there are a number of changes over previous versions of the iPhone/iPod touch SDK that suggest new features yet to be announced for the iPad.
Evidence for potential widgets
One example is the iPhone's Contact app, which is internally called MobileAddressBook. In the new iPad SDK, it has morphed into an app referred to a LittleBrownBook. SpringBoard, which is the internal name of the app that runs the Home screen icons, uses the app tag "stand-alone-contacts" for this new app.
This suggests that there will also be a non-standalone version of Contacts, or in other words a desk accessory style widget to present contact information outside of the standalone Contacts app. Mac OS X similarly provides a contact browser that can be used in other apps in addition to the stand alone Address Book app.
Enabling a way for apps to draw upon mini-apps while continuing to run would be one way for the company to skirt around the existing restrictions of the iPhone OS security model, which do not support multiple third party apps to be launched at once. How exactly this will be implemented still remains to be seen, but it does appear similar to the classic Mac OS' use of desk accessories to get around its initial limitation of only running one main application at once.
URLs for apps
A second discovery, according to the source, is that "web snippets are not opened by the Web app anymore." It appears that SpringBoard is now handling the task of routing the user's clicks on URLs to the appropriate app. This indicates that URL shortcuts for phone numbers (for dialing or texting), mail addresses (for maps), and web URLs (for the browser) could now be given an additional layer of sophistication.
URLs could even be set to launch a given third party app. For example, URLs pointing to Facebook.com are currently always opened in the iPhone's Mobile Safari browser. But with an expanded URL system, users could opt into opening Facebook.com URLs via the dedicated Facebook app.
Third parties could potentially also create their own types of URLs that direct users to their app to handle a specific type of link. Apple's opposition to Google Voice suggests that the company wouldn't be excited about redirecting phone number URLs to a third party app, however.
Mac OS X Dictionaries
A third discovery in the new iPad SDK pertains to dictionaries. The latest SDK's Library directory is said to now contain a Dictionaries folders with the six dictionaries bundled with Mac OS X, including the Apple Dictionary of company terms, the Oxford Dictionary and Thesaurus, and three Shogakukan Japanese Dictionaries.
This could indicate new word lookup features similar to those in Mac OS X, where users can both lookup and replace words and access definitions and related words contextually.
While it's possible the files are simply carried over from Mac OS X as part of the SDK and not really a part of the iPhone OS, the source says the files are actually slightly different than those used in Mac OS X because they lack the version.info component in the bundle.
Features saved for iPad launch
The idea that the iPad will undoubtedly present additional features at its actual launch date should come as no surprise, as Apple has similarly certain reserved features for other products it has announced months ahead of their actual launch, including Apple TV and the iPhone.