As per Microsoft’s Windows Mobile 10 site , the following devices will be available for Windows 10 Mobile upgrade

Lumia Windows 10

  • Lumia 430
  • Lumia 435
  • Lumia 532
  • Lumia 535
  • Lumia 540
  • Lumia 640
  • Lumia 640 XL
  • Lumia 735
  • Lumia 830
  • Lumia 930

For owners of other Lumia devices, don’t loose hope as my 1520 is running Windows 10 Mobile ( Developer Preview )  flawlessly while Lumia 1020 has also received the update recently , albeit it broke some devices .