For our Managed WordPress customers, official security updates for PHP 7.2 will end on November 30, 2020. If your site is currently running PHP 7.2, it will be automatically upgraded to PHP 7.3 on November 1, 2020. You can verify what PHP version your site is using in your control panel.
If your site has custom PHP code, including custom themes or plugins, you may need to modify your code to keep them compatible with the version upgrade. If you want to test this PHP update on any sites in your account, you can order a clone site to test the update and ensure everything is working well.
Our upstream provider Pressable has some more information about the automatic upgrade.