As we get closer to the October 5th Windows 11 release date, Microsoft have released Windows 11 to selected devices on the Release Preview channel. Build 22000.194 was released to the beta channel last week and is now on the Release Preview channel. It could be the version that ships to Windows users October 5th and Microsoft have made an ISO available for insiders wanting to do a clean install as well.
The Windows 11 update will be an optional update and only offered to devices that meet the hardware requirements of Windows 11.
The ISO can be downloaded from here.