Well Apple does have a patent for reducing the thickness of the headphone jack, but I agree they wouldn't do this just to achieve thinness alone.
I predicted this since Apple released the Lightning audio standards last year, and then the Retina MacBook came out. There's only room for two ports on the rMB, and wasting one of them on a single purpose headphone jack when that notebook demands additional connectivity and versatility is "criminal". I fully expect the revised R-MacBook to include a lightning port, instead of a headphone port, which we now know can support USB 3 speeds, as well as power and any number of other functions. It gives something like a MacBook far more versatility while also serving a dedicated purpose, as all of Apple's wired headphones will connect via lightning.
IPhone 7 comes out with a set of Lightning earbuds, Retina MacBook also replaces the headphone jack with lightning soon thereafter. Followed by every new product update thereafter.