I think we'll be seeing new Retina MacBooks today, tentatively based upon this:
https://www.reddit.com/r/apple/comments/4b7kyv/macbook_12_renew/
Basically an Apple Store employee noticed they were out of Retina MacBooks, so went in to their system to order more stock. Model was listed as discontinued, and all other Apple Stores within 250mi of his location were out as well.
Couple this with Best Buy giving deep discounts on the machines, tells me they've depleted the supply chain ahead of today.
I don't know that we'll see anything changed other than the refreshed Skylake CPUs, which may be why there have been no leaks about it, if the casing et al is identical.