Tidbits's Glenn Fleishman claims that he has heard from a number of sources that Apple is nearing an announcement "of some sort" regarding 3rd party application development on the iPhone.
Details are unknown but the announcement is expected "soon" and perhaps as early as this week.
The bits and pieces I've heard are maddeningly non-specific: I don't know, for instance, whether a full software developer's kit (SDK) will be released; what tier of Apple Developer Connection (ADC) program member you need to be (if any); and how much of the innards would be unleashed. I don't even know whether Apple is announcing that a program is coming, or the program itself.
This news comes after a number of conflicting reports about Apple's plans for future iPhone application development. At the heart of the issue is a lack of an official developer's kit for the iPhone. Instead, Apple has advocated the use of Web-based "applications" based on Javascript. These Web-applications are very limited, however, and require the user to be internet-connected during their use.
Despite Apple's stance, an active (though unofficial) iPhone development community had sprung up and deployed a number of native applications for the iPhone. The latest 1.1.1 iPhone update, however, closed the door to these unofficial applications.
A recent a report from 9to5 suggested that Apple was planning on allowing certain 3rd party developers to launch native applications for the iPhone, but in a very restricted manner. Meanwhile, Arstechnica's sources have claimed that Apple intends to keep 3rd Party iPhone application development Web-based, but is planning on introducing significant improvements, such as off-line execution, and tighter integration to iPhone functionality. It's possible that the expected announcements could be related to these improvements.
Another possibility is that this announcement could simply be related to an expected iPhone WebApp Directory that Apple appears to be compiling on their site.