Rumors thatin an upcoming iPhone OS update can continue to be filed in the rumor bin, at least based on the developer preview release of OS 4.
Bing is still nowhere to be seen in the iPhone's Safari app, or anywhere else in the preview version of the OS. Besides Google, which remains the default search engine, the only other option remains Yahoo.
It's still possible that the Apple/Microsoft deal could be under way though. And if that's the case, it could just as easily make it into a future beta of the OS, or in the version that will be made available to iPhone owners sometime this summer.
One interesting change worth noting is that Web searches are now more ingrained into the system search that was implemented in OS 3.0. Now, when doing a local search on your phone, the iPhone will spit up quick links for Web and Wikipedia searches using Safari. This could place more importance on whatever search engine you're using as the default.
During, Apple CEO Steve Jobs went into detail on how search was largely a paradigm of desktop computing, but these changes could very well be the first inklings that the iPhone is getting a system search tool that is more integrated with the Web, as competitor Google has done on its Android OS.
In the meantime, iPhone owners who are looking to get a hearty dose of Bing can download Microsoft's native iPhone app, which was.