Microsoft just confirmed that DirectX won’t require a newer GPU, and most older graphics cards will run it just fine, with the exception of a few features.
“There will be DX 11.1 cards that take advantage of a lot of the driver and software tech that we’re bringing in Windows 10, but if you want the full benefits of DX12, you’re going to need a DX12 card,” Microsoft’s Mike Ybarra said.
“While we are not yet ready to detail everything related to DirectX12, we can share that we are working closely with all of our hardware partners to help ensure that most modern PC gaming hardware will work well with DirectX12, including; NVIDIA’s Maxwell, Kepler and Fermi-based GPUs, Intel’s 4th generation (and newer) Core processors and AMD’s Graphics Core Next (GCN) based GPUs. We’ll have more to share about DirectX12 at GDC in March.”
This means that you won’t have to spend your money again on a newer GPU, unless you want to have the full power of DirectX 12. However, I’m certain that most games and application will work without a sweat even without a high end GPU.