Just FYI, I work in the tech field and I can tell you that you can download the Windows 10 installer and do a fresh install of windows 10 on any machine and use a Windows 7 - Windows 8.1 Key and it WILL ACTIVATE with the same version as the key. When installing the new install and it asks for your key, you simply enter your Windows 7 - 8.1 key and it will validate it and continue the install. I’ve done this literally hundreds of times. I can’t guarantee that this will always be the case but as of today it does work.
If you have a Windows 7 Pro Key you will get Windows 10 Pro
If you have a Windows 7 Home Key you will get Windows 10 Home and so on
Windows 8.1 Pro Key will give you Windows 10 Pro
Windows 8.1 Home Key will give you Windows 10 Home and so on.
I hope this information is helpful for those still holding out and I can’t guarantee that this will work forever so I would do it ASAP.