Google began beta testing Assistant in Turkish with select users several months ago. If you were holding your breath and hoping that the full rollout would come before the end of the year, you can sigh of relief. Turkish support is now official, though it may be rolling out slowly to users.
Google has localized several public Assistant pages in Turkish, including the "Google Asistan" main page, the Explore page with all the available functions, and the support pages. All of them say that Assistant is available on Android phones and tablets in Turkish, as well as on the iTunes App Store for iPhone users.
However, I've spent some time testing by setting up my devices to use the Turkish language, and all I get is the Screen Search feature that preceded Assistant. Even if I set English as my main language and Turkish as second, I can type to Assistant in Turkish, but it responds in English. So it seems that even though the news is official, it hasn't rolled out to everyone just yet.
If you speak Turkish or live in Turkey, give it a go and see if it's working for you. Odds are it will be available soon.
- Google Assistant