I support renaming OS X to iOS when Mac Computers can be touch sensitive. At the moment it will make customers confused:
iPhone iOS 4
Mac iOS 10.7
Makes mac look much more advanced than 4, yet it's still not touch. Little weird.
You are assuming the numbering scheme will stay the same. My take is it will for something like this.
iOS 4.x for Xserver
iOS 4.x for Macintosh
iOS 4.x for iPhone
iOS 4.x for iPod Touch
iOS 4.x for Mac TV
this Mac OS is replaced with iOS and all are in step with the same general release number.
Afterward, we will see all Apple products, in unison, roll-out iOS 5 for everything from handhelds to servers. Only the IT grunts will know or care about the differences one deployed.