In case anyone was wondering:
OpenGL on Windows 8 x86/x64: Yes
OpenGL ES on Windows 8 ARM: No
Microsoft is only allowing certain approved APIs for apps that want to run in Windows 8 ARM. While all the hardware will certainly be OpenGL ES 2.0 capable, Microsoft has and probably won't be exposing an EGL API.
Of course if you want to use Direct3D 11.1 (well with feature levels more like 9.3 since that's what the hardware is capable of) you can go right ahead.