As further proof Lexus plans to reveal a luxury minivan at the Shanghai Motor Show, the Chubu Keizai newspaper in Nagoya has reported that production of the new vehicle is slated for next year — from the translated article:

The company will start mass production in 2020 at its subsidiary Toyota Auto Body Inabe Factory (Inabe City). First of all, export and sales to China and Asia are expected. In China and Asia, the popularity of large minivans, especially among wealthy people, is overheating. While responding quickly to the spread of demand, it intends to further enhance its brand image by introducing highly competitive products.

Toyota Auto Body is responsible for producing all Toyota vans sold overseas, including the Alphard luxury minivan that should share its underpinnings with the new Lexus version.