I think you might be confusing a transition with an introduction. The very definition of transition is a change, as though from one product to another (for example, iPhone 4 to iPhone 5). To introduce an entirely new product line would not fall under the commonly understood meaning of the word "transition".
I think the Prof has it correct. I just don't see them playing word games like transition for a rev of an existing product. It has to have something more than that - they know how flakey they market is with AAPL and playing word games would be shooting them selves in the foot. Both Steve and Tim are way to sharp to even mis-state something with potentially huge AAPL consequences. I'm betting it has to do with the bye-bye to old faithful (white MacBook) and intro of its successor (probably a re alignment of the aAir, MBP, MB lineup to be bait more homogenous while still maintaining the diffs with the Pro versus consumer line.
Just my 2 scents as if anybody gave a sh*t.