Gaming Beyond DirectX?

I know a little about video game engines and such, but I thought I'd submit this to my readers to see if maybe you could help me with the gaps in my knowledge. As some may know, I'm not happy with DRM and resource heavy Windows Vista and I'm wondering what might happen in the PC gaming world when Microsoft stops selling XP. Mainly, the question is, can OpenGL completely replace DirectX 10+? Mac, Unix, GNU, Linux all use OpenGL, but looking into DirectX, it would seem it's more powerful than OpenGL when matched with the right GPU (Graphics Processing Unit.) DirectX 10 is supposed to be fast and streamlined, which is cool, but it's only on Vista. The thing is, both OpenGL and Direct X use the same Shader Model. Does that mean OpenGL has the same abilities? I speak mainly of the amazing texturing and displacement mapping now possible with engines like the Unreal Engine 3. From what I have read, that engine was built for DirectX 9 (and patched to 10) so, I don't know how viable OpenGL is on "next generation" platforms. Then again, Call of Duty 4 is on Intel Macs and doesn't seem to take a hit graphically (although I've never played it on an Mac so, I'm not an authority.) So, anyone have the skinny this stuff?