Updated models with AMD graphics options expected in early 2017.
Mac OS X 10.5.2 Not Quite Ready Yet (9C30 Seeded)
It seems clear that Apple is putting the finishing touches on Mac OS X, with accelerated developer releases in the hopes of reaching the final build. Due to the continuous bug fixing process, it impossible to predict the release date of the next update to Mac OS X. Historically, however, Apple has released the final build as quickly as one day following the last developer seed (9B18 seeded, 9B18 released).