Sony has officially confirmed that the Xperia 5 III will ship in September. This will be hot on the heels of the Xperia 1 III which is confirmed to start shipping in the US from August 19.
https://www.notebookcheck.net/Sony-announces-Xperia-5-III-to-ship-in-September-on-heels-of-the-Xperia-1-III-which-is-now-confirmed-to-ship-on-August-19-in-the-US.548678.0.html