There won't be a later update for 2016's to get Apple Carplay
Buick has announced that Apple Carplay and Android Auto will be available on the 2017 Envision. While it's not particularly important to me, I asked a Buick representative if there might be an update coming for our 2016 Premium II. Short answer: no.
He said: "While both the 2016 and 2017 have 8-inch screens, there are a few behind-the-scenes hardware updates required to enable CarPlay functionality -- different processors, different USB ports, etc. -- so no, the 2016 can't be updated later since it's more than software that's needed. 2016 does have Siri Eyes Free, which gets you the pass-through to Siri through the steering wheel, but not the visual component of CarPlay."
I didn't ask about Android Auto, but I expect it will be the same case.