In a Hidden Dimensions piece on MacObserver John Martellaro appears to be suggesting that the iPhone OS platform, or some more capable version of it developed for a tablet device, is destined to supersede the full-blown Mac environment. "Appears to be" may be the key phrase here, as that may not be what he's really saying at all, but he's at least invoking the possibility and running it up the flagpole.
Martellaro points to the relative security of legitimate iPhone apps, sold through the app store, as compared with the potentially riskier situation on the desktop, and suggests that such an arrangement may represent the future.
That's a point I'll grant, but rather than the Mac being left to flutter on the wind of widely varying approaches to application marketing and widely varying quality, I'm expecting Apple to expand the App Store to include Mac apps, not as an exclusive means of distribution, as with the iPhone, but as an option available to the developer, with the same convenient, consolidated business arrangement as on the iPhone.
The added value of such an arrangement for the end user derives both from it offering a one-stop shop and from it providing some assurance that the software they're buying won't turn out to contain a trojan. Developers will be relieved of the need to make their own distribution and payment arrangements, and guaranteed a percentage of whatever price they set for each download.
As it isn't likely to ever be the exclusive means of Mac app distribution, the rules for acceptance might actually be more strict than for iPhone apps, with emphasis on completeness and providing functionality with real value. On the other hand, without the overriding concern for maintaining the integrity of the cellular network and usability as a phone, Apple could go the other way and only insist that the applications it distributes not increase the end user's risk. Most likely it will start out with much the same collection of policies as for iPhone apps, diverging only gradually.
The App Store is and probably will continue to be driven by mobile and portable devices, but having already gone to the trouble of creating it the additional effort to expand it to include Mac apps should be minimal, and, given that many Mac apps currently retail for tens or hundreds of dollars, it could turn out to be a significant contributor to Apple's bottom line.
Assuming it happens, expect Software Update to be integrated such that it automatically offers updates to applications purchased through the Mac App Store.