Ultra universal apps?

On Wednesday it was announced the future launch of the Mac App Store: a place to buy and download applications for your Mac, similarly to the AppStore for iPhone/iTouch/iPad.

This come from the will of making the Mac benefits of the experience acquired with the iPhone and the iPad.

The question that comes now to mind is: Will we now be able to build applications for being compatible with both iOS and Mac OS X? Or at least to build the two versions from a unique xCode project.