Apple - Can I upgrade the SSD on late 2013 retina Mac Book Pro?
The current OWC PCIe SSD's for Macbook Pro Retina's 10,1/2 work for the 2012/early2013 models. Not the Late 2013 models (11,1 (13-inch models) & 11,2 (2.0 GHz 15-inch model) & 11,3 (2.3 GHz 15-inch model) ID#'s).
They claim they will release compatible upgrades "for next year". So, I guess, not until 2014. Could be sooner, I don't know the history of their estimates->outcomes of SSD releases for pre-announced/expected products.
Update (5/24/2016)
Salvation is here! OWC has released SSD upgrades for the MacBook Pro with Retina Display 13" & 15" Late 2013, 2014, and 2015