At MacWorld in January, Jobs had announced iPhone AppStore, movie rental for iTunes and then the MacBook Air. He went on to explain how the Air didn’t need many ports or a DVD drive because you could do everything over the network, even watching movies.

I felt sure I knew what “and one more thing” would be.

Instead, he ended that keynote without “one more thing.”

Will he announce it in his keynote this time at the Apple WWDC Monday?

The one thing you can’t still do with an Air without a DVD drive somewhere is to install most commercial applications. I need to do that on my Air just like I need to do it on my iPhone.

A perfect “and one more thing” would be to announce that iTunes would support application sales for Mac and Windows.

iTunes struck compromises that revolutionized the business of promoting, distributing and selling music. It wasn’t perfect, but it solved enough of the problems of labels, artists and listeners to build with iPod into a perfect storm. It could do the same for applications.

• iTunes made it easy to find all the music you want in one place.
• Made it easy to buy, even at $.99 price point — owning a song is just a click away.
• With iTunes Digital Rights Management (DRM), you could share, but only so far, and you could authorize and de-authorize computers as needed.

This sounds like what I need with my software applications. A way to get them all from one place, instantly, easy to buy at any pricepoint, and no hassles figuring out what computers I’m allowed to use them on.

Likewise, publishers of smaller applications have difficulties marketing and collecting relatively small payments. Larger applications will have problems distributing their wares if Air starts a trend to more diskless machines. Both have issues of wanting to protect their software against unauthorized copying, and the kind of universal system and compromises in iTunes could work with software.

Can I rent software like I can rent a movie? It may not make sense when a single publisher tries to do it, but if it were supported universally from one interface, perhaps there are applications that I only need for a week at a time.

What about software in the cloud? Many web apps can only monitize themselves through ad-supported models. What if I could pay $.99 and up (one time or monthly) for Software as a Service? I’d use iTunes to find and rate apps, the iTunes payment system to start an account, and to manage my subscriptions.

Would you like to buy and sell software over the air? Would iTunes/App Store make a good model?

UPDATE 12-Jun-08: Apps are the New Singles: Betting on AppStore Revenue.