Of course, not all devices will get this update right away and others won't get it at all. Each manufacturer and carrier often choose to add their custom modifications which tend to delay the official release.
When will each device get Android 4.1, either officially or unofficially, if ever?
This community wiki will list all of the known and rumored dates for devices. If you have an update make sure to follow the format that's been established, and the following guidelines:
Keep phones in alphabetical order listing the manufacturer and model
Specify if the date is confirmed or rumored and link to the source
If there is an unofficial release, link to the site where it can be downloaded
Note that devices that do not meet Google's Compatibility Definition will not receive a Google-sanctioned update. In the case of the major manufacturers and many others, that means they won't release an update at all since Google's certification is important to their business.