Look, there's simply no way Apple isn't eventually going to open up the iPhone to 3rd party support -- it's really a matter of when and how, if you ask us.
Of course, the possibility we've been most anxious about is Apple eschewing the open platform philosophy and starting to vend only "certified' apps via iTunes -- which is what 9to5Mac is now rumoring to be the case, reporting that Cupertino has brought some former Sidekick platform developers into the fold in order to whip up a mobile app sales infrastructure for iTunes.
What's more, the rumor has it things are already progressing along with EA porting games to the iPod touch and iPhone that very same closed-platform model which would leave Apple conveniently in control of app approval, distribution, and presumably pricing.
It's anyone's guess as to whether Apple will pull the trigger in just that way, but something tells us the enterprising open source community won't be so easily deterred.