In my mind, the 13" MacBook Pro is the MacBook.
I mean, back when the aluminum unibody design debuted for the MacBook Pro, back in 2008, they also updated the more expensive black MacBook with the aluminum design too (the cheaper white MacBook was still plastic). The following year they renamed it to the MacBook Pro, presumably to help distance it from its cheaper plastic sibling.
Keep the MacBook Air as an entry level machine, rename the 13" Pro/upcoming 14" model to MacBook, and the 16" remains the MacBook Pro. I know some people would hate the idea of not having a "Pro" model that's smaller, but at the same time there has always been a HUGE discrepancy in power between the 13" Pro and the 15/16", to the point that, again, I don't think it should be called "Pro".