Now that Apple has announced a desktop version of the App Store, there is much speculation on what we are actually getting. There are already quite a few OS X software marketplaces out there, though none are as polished as the iPhone's App Store.
If Apple is smart, they will likely add the Mac App Store as a way to run universal apps and release an iOS runtime platform for the desktop. Just think about it for a minute.
There isn't much unification between doing tasks on an iPhone and a Mac simultaneously, save for the apps that sync with their desktop counterparts. Here are some predictions I have about benefits of supporting universal apps on Macs.