At I/O 2017, Google said that multiple languages, including Italian and Spanish, would be arriving on Assistant by the end of the year. November has only just begun, and Spanish (Latin America), Spanish (Spain), and Italian have been officially announced for Google Assistant.
Both traditional and Latin American Spanish varieties can now be used on Assistant (as evidenced by posts on both Google Spain and Google LatAm blogs), along with Italian. When Brazilian-Portuguese became available, a notification appeared on many people's devices, and we wouldn't be surprised if the same were happening to those in Spanish-speaking countries and Italy right now.
These languages will be rolling out to eligible phones with Android 6.0+ over the next few weeks, and they'll also become available on iPhones later in the year, according to Google's The Keyword post. However, one tipster did say that Spanish (Spain) is already out today, and the wording on the LatAm blog post implies that Spanish (Latin America) may be out today too. Let us know if any of you guys are already seeing any of these languages in Assistant.