My guess ... Apple as long as I can remember doesn't make a habit of introducing everything at once. I think it's quite possible we'll only see this new mystery MacBook introduced, with Retina Display. The other hardware will get mentioned and get minimal updates the following day, Tuesday. Meaning MacBook Pro's stay the same in form with internal upgrades, processor, USB 3 ... but no Retina option. Same for the MacBook Air, just speed bumped, no Retina. The Mac Pro could be the one more thing. iMac's will get incremental updates in the coming weeks.