Apple released the 7th beta update on iOS 13 yesterday, and the update is set to release the next iPhone, the iPhone 11.
This is based on the conclusion that iOS 13 includes a screenshot titled HoldForRelease on Tuesday, September 10. Apple has been holding their iPhone event for the second Tuesday or Wednesday of September.
The dates of the previous iPhone events are September 12, 2015, September 7, 2016, September 12, 2017 and September 12, 2018, respectively. The dates of past iPhone events have been mentioned and based on the screenshot these days and above we see the news spread.