I’m very skeptical of this theory. As shown in the diagram, it just seems too complicated. The ‘classic’ MacBook Pro’s feel redundant in that lineup; Apple doesn’t care about maintaining legacy CD drives.
In fact, my thoughts were Apple was actually going to slim down further. Although this has been opposed by recent rumours of a spec-bumped 13inch model, I think that Apple will cut the 13inch Pro. That would leave the 11inch and 13inch Air, the (new) 15inch and 17inch Pro. The 17inch would be the mobile equivalent of the Mac Pro, and the 15inch becomes the mainstream high-end laptop.
I could be wrong, but I feel that arrangement makes a lot of sense. More sense than adding a whole new type of MacBook, at least.