I think, their new concept is for colors again, also USB-C, Skylake, thin bodies, batteries like in rMB 12".. all of that stuff can cause new design. R&D department have to have at least half a year to design all that stuff, to find suitable components, manufacturers (as it was with their unique SSD plates) and so on. So probably with their new IPad pro, ipencil+keyboard, appletv, iphone 7 maybe they dont spend enough resources to boost their engineering process and to present new macbook pro's bodies now.
There are no leaks. There is no inside info about macs. Because at least they have to redesign 2 bodies.
So they could update chips only soon(when there are will be ready) or present new design later. From the point of Apple's view.. they have enough time for both