Microsoft sends word that it is bringing DirectX 12 towards Windows 7 (a year before going EOL). So yeah, hell froze over? If you have updated Windows 7 there will be DX12 and the first game that can take advantage of it is World of Warcraft. But ...

Microsoft claims that the best DirectX 12 performance will always be on Windows 10, and that's because Windows 10 contains a number of OS optimizations designed to make DirectX 12 run even faster. 

Microsoft:

Today, with game patch 8.1.5 for World of Warcraft: Battle for Azeroth, Blizzard becomes the first game developer to use DirectX 12 for Windows 7! Now, Windows 7 WoW gamers can run the game using DirectX 12 and enjoy a framerate boost, though the best DirectX 12 performance will always be on Windows 10, since Windows 10 contains a number of OS optimizations designed to make DirectX 12 run even faster.

We’d like to thank the development community for their feedback. We’re so excited that we have been able to partner with our friends in the game development community to bring the benefits of DirectX 12 to all their customers. Please keep the feedback coming!

FAQ
Any other DirectX 12 game coming to Windows 7?
We are currently working with a few other game developers to port their D3D12 games to Windows 7. Please watch out for further announcement.

How are DirectX 12 games different between Windows 10 and Windows 7?
Windows 10 has critical OS improvements which make modern low-level graphics APIs (including DirectX 12) run more efficiently. If you enjoy your favorite games running with DirectX 12 on Windows 7, you should check how those games run even better on Windows 10!

Windows 7 Gets DirectX 12 Support (sort off) - Supports World of Warcraft