Apparently, there is a leaked version of Windows Phone 7.5 Mango build 7720 available. There have been reports of success in this XDA thread, but we’d suggest proceeding with extreme caution before updating. One of the requirements will be Zune 4.7, so those with 4.8 beta will need to revert back.
My edit of the instruction file:
Caution: Do this at your own risk, no one is to blame if your update fails
-Phone with Nodo (7392), Mango 7661 (Beta) or Mango 7712 (Developer Beta)
-PC with at least 20 GB of free disk space on C:
-external hard drive or USB flash drive with up to 16 GB of free space
-1.5 – 2 hours
1. All contents must be extracted to a local disk, not a backup/external disk.
2. Install the zune beta client version 4.8.2134.0 (comes with the downloaded file)
3. If necessary, run the flashing tool “updatewp” from the folder “update tool” install right version for your system, 32 – or 64-bit
4. Connect Device via USB to the PC
5. Close Zune software, if it opens when connecting
5a. —-If your device is allready using 7661 or 7712, go to Step 16
6. Open the “NoDoToRC” folder and run the file “ISV_Provisioning_Live.exe” with admin rights (right click on the file..)
7. The tool will now create a backup of the phone. This takes quite some time, depending on how much you have installed on your device.
8. The phone will reboot and are starting communication with a “special” update server. If necessary, enter PIN code if activated on your device
9. Please dont close the update tool until it say its finished.
10. In the directory “C: \ Users \ \ AppData \ Local \ Microsoft \ Windows Mobile Update,”there should be the newly created backup folder with a cryptic name. Please feel free to copy the folder to a secure location (external hard disk, etc.) and keep safe!
Repeat to yourself many times: “Yes, I have copied my backup to a secure location”
11. Now start the Zune client (with your phone connected) and it will begin looking for updates.
12. Build 7403 will now be found found and installed.
13. After 7403 has finished updating, the update is moving seamless to 7712 – the public developer beta.
14. If everything is done properly: Congratulations, the phone is in now running build 7712
15. Close/exit Zune.
everythingWM.com is not responsible for your phone should things not work.
For those daring enough to try, please let us know how it works for you in either the comments below or our Windows Phone 7 Forums.