Does this indicate that the upcoming SDK may offer a Mac-based developer simulator, an "iPhone in a box?" One would certainly hope so, and it would allow iPhoneless programmers to begin work immediately without buying devices -- but with Apple it's sometimes hard to tell where things are going. With this SDK everyone is playing their cards especially close to the vest. There's been a lockdown on the rumor channels, and the small trickle of iPhone inside intelligence has been squeezed dry. A simulator would certainly help developers begin their iPhone projects even before any iTunes app-shipping solution had been ironed out.
We know a rather full suite of iPhone development support was in place long before the first unit shipped. There have always been fleeting references to the Shark performance monitoring system that's a Mac OS X standby. Perhaps a full debugging suite (a lot better than printf statements) will accompany the SDK as well.
Speaking of the rumor trickle, the big one that I'm hearing right now is about big SDK delays -- perhaps all the way to WWDC (which makes us think that the big Apple show coming up may not be for the iPhone). It sounds like putting together a public SDK, documented and tested for third-party use, is a huge, huge project, and that Apple is busy hiring people to make this happen. On the other hand, Apple rumors are...unreliable. Could be that Apple is right and ready to ship end of February, exactly as promised at MacWorld.
Something that may slow down the release--if these rumors are credible--is Apple's desire to exercise the greatest amount of security-based control over exactly what the developers will and will not be able to do with that SDK. Although many have assumed that 3rd party developers will be able to build applications similar to the ones currently shipping for jailbroken iPhones, Apple has never announced what form the SDK will take.
Expect an iPhone developer revolution if Apple ships a sandbox, but don't be shocked. And don't be surprised if a simulator allows Apple to delay the release of third-party apps via iTunes for months to come.