Wouldn't OpenGL in addition to OpenGL ES allow for greater performance in things like high graphics gaming and what not?
Applications don't care what support Wayland has, that's why you can still use 3D apps on a strictly 2D desktop. So you'll be able to use OpenGL 4 in games no matter what Wayland is doing.
The only things it really affects are Compiz and Kwin (and other compositors). These will need to be rewritten to work on OpenGL ES, which is basically the same as OpenGL 3 minus all the fixed-function backwards compatibility. It might be missing a few of the newer OpenGL features, but I suspect those will be included as extensions if they aren't already. I think it's good to only guarantee the base ES2.0 functionality anyway, so that the code can also run on mobile devices that only support that much.
Wayland requires apps to use OpenGL ES because there's no actual way to create an OpenGL context on Wayland right now. Normally, to create an OpenGL context, you need to use some windowing-system-specific API, such as GLX (X11), WGL (Windows), or AGL (Mac). Wayland doesn't implement any of these for obvious reasons, instead preferring that applications use EGL.
EGL supports OpenGL, but if I understand correctly it's only really implemented for OpenGL ES and OpenVG in Mesa right now.
This is entirely a short term and fixable problem, not a huge show stopper of any sort.