Google Ads has announced they are delaying the removal of the accelerated delivery option from September 17, 2019 to October 7, 2019. This gives you an additional 20-days to prepare your campaigns and stop using this accelerated delivery option.

Google announced that accelerated delivery was going away on September 17th back on August 19th. But Google now said "To give you more time to prepare, these campaigns and budgets using Accelerated delivery will be automatically switched to Standard delivery, starting October 7, 2019. Accelerated delivery will no longer be available after this change."

So you have a bit more time to prepare for this change.

I am not sure why 20-days makes a huge difference but hey.

Forum discussion at Google Help.