For me, that was the big question during Steve Jobs’s keynote address at Apple’s Worldwide Developer Conference, and it’s still unanswered. Sure, Apple and its partners made a flurry of interesting announcements, including the 3G iPhone everyone expected. Several of the announcements even involved slick-looking new iPhone software. But was any of it groundbreaking for a mainstream audience? Hardly.

I’ll admit that I’m holding Jobs to a high standard. Under his leadership Apple has been on a tear, mastering the market for music players, gaining share in PCs, and shaking up the cell phone industry. Jobs has led the company so effectively that right now the iPhone, the linchpin of Apple’s growth strategy, faces a critical test: Will it redefine the mobile industry, giving Apple the sort of clout in phones that Microsoft has in PCs? Or will it simply occupy a high-fashion niche, and leave the real profit making to others?

The difference between a dominant or dwindling iPhone will be software. Or more plainly, the ability of Apple and other software companies to make the iPhone do amazing things that couldn’t be done before. Jobs & Co. have achieved this feat at least twice in the past. The first time, with the original Mac, Apple joined with Adobe Systems and others to usher in the era of desktop publishing, allowing people to create and print professional-looking documents with a computer. The second time, with the iPod and iTunes, Apple worked with the recording industry to offer the first intuitive system for acquiring, organizing, and listening to music.

The iPhone hasn’t yet proven it has the same spunk. It does a beautiful job surfing the Web, but that’s a cool feature, not a killer app. It’s handy for corporate e-mail and address books, but Research in Motion’s (RIMM) Blackberry got there first. It’s got multimedia features, but so does my iPod.

For this device to truly fulfill its potential, I believe it will have to offer something totally new – something like on-board photo and video editing, or a videoconferencing app, or (most likely) something too cool for me to dream up. By reaching out to software developers, Apple has put itself and its partners in position to achieve that kind of breakthrough eventually – but I didn’t see it this morning.