[Updated 26/05/17 this still works]
Reportedly you can still get a Windows 7 (or 8) - Windows 10 free upgrade the following way:
(Requires **erasing your PC** and some advanced knowledge of boot selection and install procedures, only for power users and make your own investigations before attempting this)
- Ensure that you have your Windows 7 install product key, normally on a sticker on your PC or laptop case
- Download the Windows 10 Creators edition install disk image here: https://www.microsoft.com/en-au/software-download/windows10 (make sure you get the correct version based on the version that you are upgrading from Pro or Home for example)
- Make the DVD or USB boot device using the tool that you downloaded above
- Boot from the DVD or USB Erase the drive and Install Windows entering your Windows 7 product key when prompted
- When windows finishes installing Windows 10 should activate with the windows 7 key
I expect this opportunity will only be for a limited time MAKE YOUR OWN INVESTIGATIONS BEFORE ATTEMPTING THIS.
THIS INFORMATION PROVIDED WITHOUT WARRANTY OR OFFER OF FREE SUPPORT.